http://localhost:8081/jspui/handle/123456789/23 2025-06-29T15:23:15Z 2025-06-29T15:23:15Z Singh, Prashant Kumar http://localhost:8081/jspui/handle/123456789/15794 2024-09-30T06:27:22Z 2020-01-01T00:00:00Z

Title: GENERATION OF HYDROGEN FROM SODIUMBOROHYDRIDE USING VARIOUS CATALYSTS AND ADDITIVES FOR FUEL CELL APPLICATIONS Authors: Singh, Prashant Kumar Abstract: The cobalt boride is used as catalyst for various important chemical reactions such as hydrogenation of alkenes, citral, aldehyde, and reduction of nitrogen oxide, water splitting reaction, ODH of propane, Oxygen Evolution Reaction, Na-O2 batteries, and hydrogen generation. The unsupported and supported cobalt-boride catalysts have been prepared by considering various method of synthesis. The supports used for the synthesis of supported catalysts are ceria, carbon nanotubes, activated carbon, silica, titania, and alumina. The active component of these catalysts is cobalt-boride and the species dispersed over the support differently. The objectives of the present thesis work were to study the generation of hydrogen from sodium-borohydride using various catalysts/additives for fuel cell applications. The generation of hydrogen was considered by a) hydrolysis of sodium borohydride solution using supported/bulk metal-boride catalysts, and b) thermolysis of sodium borohydride using metal halides additives. Metal-boride catalysts were active for the hydrolysis of sodium borohydride at room temperature. The bulk metal-boride catalysts (CoB, NiB, and FeB) were synthesized by simple reduction precipitation method. The supported metal boride catalysts (CoB/SiO2) were synthesized by two-step reduction precipitation followed by impregnation method. The surface area of the metal-boride catalysts was also increased by using various support materials. Since the metal-boride catalysts are not active for thermolysis of sodium borohydride for the generation of hydrogen. The metal halide additive/catalysts composite mixtures were active for the thermolysis of sodium borohydride at low temperature. The metal-halides additives/catalysts were used for the thermolysis study are MnCl2, CaCl2, and ZnCl2. The sodium-borohydride/additive composite mixtures were prepared by facile solution method. The ii bulk (CoB) or supported metal-boride (CoB/SiO2) catalysts or the composite mixture (xMnCl2/NaBH4) were characterized using various characterization techniques to improve our understanding of hydrogen generation from sodium borohydride by considering various factors such as metal loading, effect of calcination temperature, effect of supports of catalysts, and the effect of thermolysis temperature to find the most suitable additive. Moreover, the synthesized catalysts and composite materials were characterized by BET, XRD, FE-SEM, in situ UV-vis spectrophotometer, FTIR and Raman spectroscopy. A series of CoB, FeB, and NiB catalysts were prepared by the chemical reduction method using base stabilized sodium borohydride solution as a reducing agent. The CoB catalyst was most stable and highly dispersed even at high calcination temperature. The hydrolysis study suggested that CoB catalyst was most effective and suitable for the generation of hydrogen from hydrolysis of sodium borohydride. The generation of hydrogen using base stabilized CoB-BS catalysts was most active using both the base/without base stabilized sodium-borohydride solution. The generation of hydrogen using base stabilized sodium borohydride solution using various catalysts was as follows: CoB-BS > NiB-BS > FeB-BS. The effect of support on the CoB catalysts were examined and studied. The supported cobalt boride catalysts (xCoB/SiO2, xCoB/Al2O3, xCoB/MgO) were prepared by two-step impregnation-reduction method. The synthesized catalysts were studied for the hydrolysis of based stabilized sodium-borohydride solution for the generation of hydrogen. The synthesized catalysts were characterized by using BET, XRD, and Raman spectroscopy techniques. Various parameters such as catalysts loading, effects of calcination temperature, effect of supports were considered. The synthesized catalysts were calcined at various calcination temperature from 373 K to 773 K. The study suggested that the support plays a significant role on enhancing the generation of hydrogen from base stabilized sodium borohydride solution. Moreover, the calcination temperature also played a significant role in enhancing the catalytic iii performance. It was necessary to calcined the CoB impregnated support at moderate temperature before reduction of the cobalt so that an active CoB is dispersed and anchored with the support properly. The study suggested that the surface area gradually increased with increasing calcination temperature up to 573 K and furthers increasing calcination temperature the surface area decreased for the catalysts xCoB/(support). However, all the calcined samples were highly amorphous in nature even at 673 K and started formation of crystalline phase at 773 K in 50CoB/Al2O3. It was also observed that a Co3O4 species formed with the CoB in all catalysts during the second step of catalyst synthesis (reduction step). The most active catalyst was found to be 50CoB/SiO2 calcined at 573 K. The order of catalytic activity for the generation of hydrogen for all catalysts: 50CoB/SiO2 > 50CoB/Al2O3 > CoB > 50CoB/MgO. The effect of additives/catalysts for the thermolysis of sodium borohydride is also important for the generation of hydrogen. A series of MnCl2 impregnated sodium borohydride composite mixture was prepared by facile solution method at room temperature. The additive loading was varied from 10 wt% to 50 wt% during the synthesis of composite materials. Other additives were also used such as CaCl2 and ZnCl2. However, the 20 wt% of additive was an optimum loading for the synthesis of 20MnCl2/NaBH4 composite mixture. The generation of hydrogen was obtained from the material 20MnCl2/NaBH4 at 373 K. The generation of hydrogen increased with increasing thermolysis temperature (373 K to 823 K). However, the study suggested that the generation of hydrogen was incomplete at 373 K from the material 20MnCl2/NaBH4. The most effective additive was found to be CaCl2. The addition of additive assists in lowering the thermolysis temperature of NaBH4 for the generation of hydrogen. The effect of additive considering various additives as as follows: 20CaCl2/NaBH4 > 20MnCl2/NaBH4 > 20ZnCl2/NaBH4. The FTIR analysis and thermolysis study suggested that the generation of hydrogen was incomplete at low temperature (373 K). iv Thus, the generation of hydrogen from sodium borohydride (hydrolysis/thermolysis) using various catalysts (supported/bulk) and metal-chloride additives with the information obtained from various characterization studies of BET, XRD, FTIR, FE-SEM, and Raman spectroscopy, the effect of various parameters could be established. The parameters included the effect of metal in metal boride catalysts, effect of calcination temperature, effect of supports, and effect of various additives.

2020-01-01T00:00:00Z Lone, Sohail Rasool http://localhost:8081/jspui/handle/123456789/15793 2024-09-30T06:38:57Z 2020-02-01T00:00:00Z

Title: MASS TRANSFER ASPECTS OF CELL CULTURE IN A BIOREACTOR Authors: Lone, Sohail Rasool Abstract: The widespread use of stirred tank bioreactors (STBRs) with agitation system as their core elements can be explained by their long tradition. STBRs being multiphase reactors are most widely used in industrial applications including chemical, biochemical, pharmaceutical and biological processes owing to their excellent operational flexibility and mixing capability. They play a vital role in the biopharmaceutical industry, particularly in aerobic bioprocesses and can find applications in fermentation and cell culture systems. STBRs have attracted much greater attention in the bioprocesses owing to their potential for integrating the development of high value-added products and thus replacing the need for conventional chemical based processes. STBRs have huge industrial importance as nearly 50% of the chemical reactants and products have passed through stirred tank reactors at one stage or the other and thus translating into over USD 1200 billion turnover per annum worldwide. To enhance the heat and mass transfer in such systems, baffles and impeller and other internals for specific applications are used. The oxygen transfer in such systems is an important parameter for determining their efficiencies and successful scale-up and is generally characterized by volumetric mass transfer coefficient, kLa being recognized as the most important parameter characterizing gas-liquid mass transfer in STBRs. It also serves as an important transport characteristic used in the scale-up, design and performance optimization of STBRs. The oxygen transfer is often considered as a rate limiting factor for the bioprocesses due to its low solubility in the liquid medium and therefore controlling dissolved oxygen in the liquid medium, i.e. broth is essential for cell growth. It is generally affected by agitation or (stirring) rate, aeration or (air flow rate) rate, media properties, different impeller types and their configurations, etc. Power consumption is also very important parameter in STBRs. It is an indispensable and the mostly used parameter to describe hydrodynamics, mixing and mass transfer and is also important scaling up parameter in stirred tank reactors. In this work, experiments have been carried out in stirred tank bioreactors of different volumes, i.e. 7.5 L, 5 L and 1 L. Dissolved oxygen concentration for the prediction of volumetric mass transfer coefficient, kLa has been measured by using the most widely used physical method, i.e. dynamic gassing-out-gassing-in method. It was observed that with an increase in scale of the reactor, irrespective of the impeller configuration, the kLa decreases when employing the same iii agitation speed (50-800 rpm) and aeration rate (0.5-3.5 L/min.). The effect of other parameters such as impeller diameter, liquid volume inside the reactor, liquid medium viscosity on kLa has also been studied. The power input per unit volume is also studied for single and dual Rushton turbine systems. It is observed that the power consumption in aerated system is lower than the unaerated system, because the transfer of power from impeller to the fluid is greatly influenced by aeration. It may also be attributed to the formation of cavities behind the impeller blades and the fluid having different density under gassed and ungassed conditions. The difference between gassed and ungassed power inputs is more pronounced at higher agitation rates (400-800 rpm). A new correlation has been proposed for kLa and P/VL based on a mathematical and statistical approach using response surface methodology (RSM) with Box-Behnken design (BBD) of experiments. This correlation includes the effect of various parameters such as agitation rate (50-800 rpm), air flow rate (0.5-3.5 L/min.) and temperature (10-40 °C) for different impeller configurations. Among the operating parameters, the most significant variable affecting kLa was found to be agitation rate, followed by aeration rate and temperature. The effect of temperature in most cases was insignificant. This may be most likely due to the range of temperature examined in this study was relatively narrow, typically used in commercial bioreactors. Among the investigated impeller configurations, dual Rushton turbine demonstrated the highest value of kLa. However, taking into account both kLa and shear force generated by agitation, the pitched blade turbine appears to be most effective for aerobic fermentation and cell culture applications. Models developed using RSM successfully interpreted experimental kLa and have been further validated under other operating conditions. More importantly, it is also observed that, compared with conventional power-law models, the RSM approach enables a more efficient correlation procedure and formulates simplified models with comparably high accuracy. Further to study the effect of impeller spacing on kLa and power input per unit volume (P/VL), RSM-BBD study has been carried out considering three factors, i.e. agitation rate (100-600 rpm) and aeration rate (1-12 L/min.) and impeller spacing (4-8 cm) for dual Rushton and mixed impeller (Rushton-marine propeller) configurations. It is found that kLa and P/VL were mainly affected by agitation rate, however the interaction between agitation rate and aeration rate is significant for both configurations. It is also observed that the effect of impeller spacing on kLa and P/VL was insignificant. Correlations developed using RSM for P/VL have been found to better predict as compared with the available correlations in the literature. It is also established that P/VL is lower iv for mixed impeller, thus suggesting its wide applicability in cell culture applications. A new power-law correlation is proposed for the mixed impeller configuration. Higher level of accuracy for both the original and simplified RSM models is observed as compared with conventional power-law models. Finally, the proposed simplified models successfully validated with the experimental data. A power-law correlation proposed for dual Rushton turbine has been found to well predict kLa and comparison has also been made with the available correlations in the literature and the RSM models, both original and simplified. Further, mass transfer and rheological behavior are characterized during the growth of E. coli BL21 in a stirred tank bioreactor. During the culture of E. coli BL21 in a 1 L stirred tank bioreactor, effects of various key operating variables such as agitation rate (50-600 rpm), aeration rate (0.5-2 L/min.), impeller diameter (4-5 cm), bioreactor working volume (0.25-0.75 L) for different impeller configurations on kLa has been investigated. It is observed that kLa increases with all the examined operating variables except the bioreactor working volume. Among the impeller configurations investigated, pitched blade turbine showed the highest kLa value (2.72 min-1), suggesting that it is promising for its successful cell culture as it also generates relatively less shear force owing to its low power number. A comparison evaluating mass transfer with and without cells has also been investigated in this study. A new impeller type, i.e. dislocated Rushton turbine has been investigated for its mass transfer performance having same dimensions as that of the standard Rushton turbine and is found to display superior mass transfer performance for E. coli BL21 culture, thus showing its potential for its application in bioprocess industry. Further, kLa for different impeller configurations is also correlated using dimensionless groups such as Reynolds, Froude and Flow numbers, suggesting this approach can be used for predicting kLa in different scale of stirred tank bioreactors. To understand rheological properties of the culture medium, in the present work, samples of the liquid medium with a dual Rushton turbine have been collected at specific time intervals, and their viscosity is evaluated. The rheological analysis showed that the viscosity of the liquid medium used in this study is independent on the shear rate, indicating that it behaves as a Newtonian liquid. Further, it is also observed that the shear stress linearly increases with the shear rate, which indicates that the liquid medium can be classified as a Newtonian liquid.

2020-02-01T00:00:00Z Garg, Deepak http://localhost:8081/jspui/handle/123456789/15792 2024-09-30T06:40:25Z 2020-02-01T00:00:00Z

Title: REMOVAL OF ACID YELLOW-36 & DIRECT BLUE–86 USING PEANUT SHELL ACTIVATED CARBON FROM WASTEWATER Authors: Garg, Deepak Abstract: Water is an important component for existence of all living beings. Since the beginning of civilization, mankind flourished around the sources of water. With the skyrocketing growth in population, climatic changes and industrialization, availability of fresh water on earth is declining continuously, on the other hand demand is enlarging. After industrialization our water sources such as oceans, rivers started squeezing in quality, due to anthropogenic activities which have led to degradation of environment. Survival of living beings is threatened and earth’s support system is endangered due to Pollution. Worldwide leading cause of diseases and deaths is due to water pollution. Water is contaminated by numerous inorganic and organic substances such as industrial wastes, fertilizers, toxic chemicals, metals, dyes and its byproducts. Dyes are organic compounds used as colouring material in various industries mainly textiles. Dyes transmit colour to water and a small fraction is easily recognizable, which is aesthetically unacceptable. Due to complex structure, dyes are difficult to degrade. Abundant production of dyes have undesirable environmental effects. Despite the adverse effects caused by dyes to the environment, they are continuously being discharged in water bodies thus disturbing the water cycle. The condition can further intensify without strict remedial action. Thus, prioritizing wastewater treatment is essential to avert crippling water problems. Today world is becoming more eco sensitive which has given new impetus to waste water treatment. Researchers are in constant search of technically feasible and economically viable methods for removing dyes and its toxic effects from the environment. There are different methods that are used for the removal of dyes from wastewater amongst them adsorption has been found to be more advantageous and effective method. Adsorption is easy, reliable and versatile method for the removal of dyes. Over the past few years, trend of using ecofriendly, low cost adsorbent has increased. Focus of this study is on the adsorptive removal of two anionic dyes: Acid Yellow-36(AY-36) and Direct Blue-86 (DB-86) from aqueous solution using low cost activated carbon as adsorbent. So for present study, an agricultural waste, peanut shell was used as raw material for manufacturing peanut shell activated carbon (PnsAC) using H3PO4 as chemical activator. The pyrolysis is carried out under nitrogen environment at a ramp of 10 oC min-1 upto a temperature of 650 oC for 2 hr activation time. iii To test the efficacy of PnsAC different characterization studies were performed. Thermal stability was analyzed using TGA technique. Surface morphology was studied by SEM images and elemental analysis was carried out using energy-dispersive X-ray spectroscopy (EDS). Variation in surface functional groups were interpreted by Fourier Transform Infrared spectroscopy (FTIR). Zero point charge for PnsAC was 2.3. Investigations were done for studying the adsorption potential of PnsAC for the removal of anionic dye AY-36. Batch experiments were conducted to study the effects of pH (2 – 11), adsorbent dose (2 – 6 g L-1), and initial AY-36 concentration (100 – 250 mg L-1). The optimized condition obtained by varying the variables were obtained at temperature 35 oC, initial dye concentration 200 mg L-1, pH 2, PnsAC dose 4 g L-1 and equilibrium time 150 minutes. 98 % removal of AY-36 was achieved at optimized conditions. Equilibrium adsorption isotherms, kinetics, and thermodynamics were investigated. The experimental data were analyzed using different isotherm models: Langmuir, Freundlich, Redlich–Peterson, Sip, and Toth. The kinetics of adsorptive removal of dyes was studied with Pseudo first order, Pseudo second order and intraparticle diffusion model. Equilibrium study revealed that Freundlich isotherm model described best the experimental data. The kinetics of dye adsorption was found to confirm Pseudo second order kinetics with a correlation coefficient value of 0.999. Kinetic study results indicated that the chemisorption likely dominated the adsorption of AY-36 on peanut shell activated carbon (PnsAC). Thermodynamic study revealed that the adsorption process was feasible, endothermic and spontaneous. Another dye DB-86 was adsorbed using PnsAC. Adsorbent dose of PnsAC was investigated through batch experiments at various initial pH and DB-86 concentration, to obtain maximum adsorption. This study showed that 78.6 % removal was obtained for 10 g L-1 PnsAC dose in 150 minutes (equilibrium time) at pH 2, while temperature was maintained at 35 oC. Kinetic, equilibrium, and thermodynamic studies were carried out to validate the results from experiments. Kinetic study confirms that the adsorption phenomena follow the Pseudo second order rate equation. Isotherm study reveals that Freundlich, Redlich–Peterson, Sip, Radke– Prausnitz, Koble-Corrigan, and Fritz–Schlunder isotherm models well explained the experimental equilibrium data. Thermodynamic study showed a negative value of ΔG° which advocated that the process of adsorption was spontaneous. Positive values of ΔH° and ΔS° signified the endothermic and increased disorderness in the adsorption of DB-86, respectively. Further, for effective adsorption, PnsAC was modified with alginate and used for the removal of DB-86 dye. The alginate encapsulated activated carbon (PnsAC-alginate), prepared from waste iv peanut shell was used as an adsorbent. Alginate encapsulation was done by pouring homogenous mixture of sodium alginate and PnsAC into the bath of 1 % calcium chloride solution. The effects of temperature, equilibrium time, adsorbent dose, dye concentration and solution pH on the adsorption of DB-86 onto PnsAC-alginate were studied. To the best of our knowledge, no attempt have so far been made for optimization purpose using response surface methodology (RSM) in the adsorptive removal of DB-86. Central composite design coupled with RSM was used to optimize the adsorption feed conditions in order to achieve maximum dye removal efficiency. The statistical analysis revealed that for maximum dye removal efficiency, the optimal conditions were adsorbent dose of 24.65 g L-1, DB-86 dye concentration of 125.5 mg L-1 and pH of 3.1. Under optimized conditions, experimental dye removal efficiency (98.4 ± 0.1%) agreed closely with the predicted results, thus indicating the suitability of RSM in optimizing the feed conditions. SEM, EDS, TEM, XRD, BET and FTIR analyses showed the surface morphology of the adsorbents and confirmed the adsorption of DB-86 onto PnsAC-alginate. Crystalline behavior of PnsAC-alginate were analyzed using X-Ray diffraction (XRD). Zero point charge for PnsACalginate was 7.8. The experimental results also showed that the dye removal efficiency was increased by 7 % compared to that with peanut shell activated carbon (PnsAC) as an adsorbent. The adsorption kinetics of DB-86 was well described by Pseudo second order kinetic model with intra-particle and film diffusion mechanisms. Langmuir isotherm model provided the best fit to the adsorption equilibrium data, obtaining maximum dye adsorption capacity of 21.6 ± 0.9 mg g-1. Estimation of thermodynamic parameters revealed that the adsorption process was feasible and was spontaneous and endothermic in nature. The present study has demonstrated that the use of positively charged PnsAC-alginate as an adsorbent is a cost effective and suitable alternative for the removal of anionic DB-86 dye from aqueous solutions. From above study we can conclude that, low cost adsorbents PnsAC and PnsAC-alginate can be commercially converted into efficient adsorbents for the removal of AY-36 and DB-86 dyes from aqueous solutions by adsorption.

2020-02-01T00:00:00Z Tsegaye, Bahiru http://localhost:8081/jspui/handle/123456789/15791 2024-09-30T06:42:06Z 2020-01-01T00:00:00Z

Title: STUDIES ON BIOCONVERSION OF LIGNOCELLULOSIC BIOMASS TO BIOFUEL Authors: Tsegaye, Bahiru Abstract: In today’s world, fossil fuel (petroleum, natural gas, and coal) is one of the major sources of energy. The global demand for energy is growing each year along with population growth. However, climate changes caused by the use of fossil fuels and its limited availability and sustainability are driving for search of a sustainable supply of energy. The sustainability problem of fossil fuels and the emission of greenhouse gases open the doors for scientists to search for a sustainable and relatively safer supply of energy to the world. The aim of this research was to isolate, identify and characterize novel bacteria having lignocellulosic potentials (lignin, cellulose, and hemicellulose depolymerizing ability) from termite guts. The performance and the capabilities of the microbes were evaluated on lignocellulose biomass (wheat straw, rice straw and sorghum straw) after isolation and application of microbes on the model compounds. The delignification and hydrolysis efficiencies of the bacteria were evaluated simultaneously and separately. The polysaccharide hydrolysis efficiencies of the microorganisms were also evaluated by combining microbial hydrolysis with NaOH pretreatments, Organosolv pretreatment and microwave assisted NaOH pretreatment. The microorganisms were screened and identified by subsequent plate culturing and 16S rRNA gene sequencing. The growth conditions for the isolates were optimized experimentally. Using the optimized conditions, the delignification capabilities, polysaccharide hydrolysis capabilities and efficiencies were investigated experimentally in simultaneously and separately system. The compositional analysis of the biomass before and after pretreatment processes were studied to observe and understand the changes in composition and to know the extent of degradation due to the pretreatment process. The pretreated and raw biomass were characterized by field emission- electron microscopy (FE-SEM), X-ray diffractometer (powdered XRD) and Fourier transform infrared spectroscopy (FTIR). The extent of polysaccharide hydrolysis was investigated by measuring the amount of reducing sugars released per unit time. The reducing sugars were measured by 3, 5 dinitrosalycilic acid method. In this study, two different bacteria strains, Bacillus sp. BMP01 and Ochrobactrum oryzae BMP03 strain were isolated and identified from termite guts which have lignocellulose degrading capabilities. Bacillus sp. BMP01 strain has capabilities to hydrolyze carboxymethylcellulose and xylan to glucose and xylose, respectively. This strain showed high xylanase activity (about 0.21 U/mL) and carboxymethyl cellulase activity (about 0.25 U/mL). Ochrobactrum oryzae BMP03 v strain showed laccase activity, which indicates its ability to depolymerize lignin. This result demonstrated that the guts of termites comprise of lignocellulose degrading bacteria that can be cultured and grown in a bioreactor and can be used for the production of vital chemicals like bioethanol. Biological conversion of rice straw, wheat straw and sorghum straw were studied by applying the isolates. The maximum lignin removal was observed after the 14th day of rice straw biotreatment in separate delignification and hydrolysis process (about 53.74% lignin removal). About 69.96% of total reducing sugars were obtained after the 14th day of hydrolysis of biodilignified rice straw. In simultaneous delignification and hydrolysis process, about 58.67 % of total reducing sugars were obtained after the 13th day biotreatment. The lignin degrading bacteria preserves polysaccharides (cellulose and hemicellulose). Biodelignification followed by microbial hydrolysis of wheat straw increased the amount of total reducing sugars and biofuels yield. It was shown that the production of total reducing sugars in separate hydrolysis system by Bacillus sp. BMP01 strain achieved 439 mg / g at 16th days of hydrolysis time, which is 9.45% higher than the simultaneous system. About 44.47% lignin was degraded by Ochrobactrum oryzae BMP03 strain after 16th days of biotreatment. This also contributed to increase in cellulose content by 22.38% and hemicellulose content by 18.64% after biodelignification. The simultaneous system converted 368 mg of reducing sugars/ g of wheat straw. About 64.29% of lignin from sorghum straw was removed after 14th day of biotreatment while 48.45% increase in cellulose and 22% increase in hemicellulose after biotreatment were found. About 69.81% of total reducing sugars were obtained after the 14th day of hydrolysis of biodilignified sorghum straw. In simultaneous delignification and hydrolysis process, about 54.52 % of total reducing sugars were converted after 14th day biotreatment. Separate biodelignification and hydrolysis have an advantage over the simultaneous system in terms of hydrolysis efficiency and vice versa in terms of biotreatment time. The study showed the possibilities of biological conversion of lignocellulose biomass to its monomers by bacteria from termite guts. The combination of sodium hydroxide pretreatment with microbial hydrolysis has significant capacity for biofuel production. Pretreatment in 3% and 7% sodium hydroxide concentration at 80 0C were effective in removing 67.13% and 71.29% of lignin, respectively from rice straw. 70.56% and 71.33% of cellulose were preserved after 3% and 7% pretreatments, respectively due to solubilization of high amount of lignin and hemicellulose. 88.27% and 88.40% of all the vi polysaccharides were converted to glucose and xylose after subjecting to microbial hydrolysis. In case of wheat straw, 10% NaOH pretreatments on wheat straw biomass leads to effective cellulose release (72.67%) and solubilization of significant amount of hemicellulose (55.55%) and lignin (69.5%). Maximum conversion of polysaccharides (83.68%) to glucose and xylose were observed at 10% NaOH pretreated wheat straw after subjecting to microbial hydrolysis. In case of sorghum straw, the maximum amount of lignin removal (78.20%) were observed after 5% sodium hydroxide pretreatment and also maximum polysaccharide releases (76.29%) were observed. About 820 mg of reducing sugars /g of biomass were released (91.27% conversion) after 13th day of hydrolysis. Microbial sources from termite showed great potential to replace commercial enzymes. Generally, the study revealed the enhancement of bioethanol production by coupling alkali pretreatment with microbial hydrolysis and fermentation. Organosolv pretreatment of rice straw, wheat straw and sorghum straw were studied for maximum cellulose release and lignin solubilization and minimum hemicellulose decomposition at pretreatment temperature from 60-1000C, treatment time from 10-50 minutes and acid concentrations from 50%-90%. In the case of rice straw pretreatment, optimized condition was achieved at 780C, 69.5% acid concentration and pretreatment time of 32 minutes. At this condition about 73.73% of lignin was removed, 74.65% of cellulose released and 52.66% hemicellulose preserved in the residues. Exposure time has found to be more influential factor than acid concentration and temperature during rice straw depolymerization. Hydrolysis of the pretreated straw resulted in conversion efficiency of 62.09% (515 mg/g of rice straw) using Bacillus sp. BMP01. Fermentation of hydrolyzed straw resulted in 0.38 g of ethanol/g of reducing sugars after 96 hours of fermentation (Ethanol yield of 74.46%). In the case of wheat straw pretreatment, optimum pretreatment condition was achieved at temperature of 790C, 69.5% acid concentration and 29 minutes of exposure time. At this pretreatment condition, 69.42% lignin was removed (5.55% remained in the residue), 74.13% cellulose was released and 13.54% hemicellulose was preserved (67.26% of original hemicellulose was preserved). About 70.22% of conversion efficiency (684 mg/g) was achieved after 10th day of hydrolysis. Ethanol yield of 0.417 g/g of total reducing sugars was obtained by fermentation of the hydrolyzed straw. This study revealed that Organosolv pretreatment followed by bacterial hydrolysis could be a potential alternative for the vii conversion of rice straw, wheat straw, sorghum straw and also with possible extension to other agricultural residues to enhance reducing sugars yields and ethanol yields. Response surface methodology (RSM) based on central composite design (CCD) was used to design experiments and to optimize experimental conditions for efficient depolymerization of rice straw, wheat straw and sorghum straw using microwave assisted NaOH pretreatment method. Temperature from 1200C -2000C, NaOH concentration from 0.5%-2.5 %, w/v, and pretreatment time from 5- 25 minutes were considered at five different levels. In the case of rice straw, NaOH concentration is found to be the most influential factor to ensure efficient depolymerization of the straw. At optimal pretreatment condition (temperature 1600C, time 15 minutes and NaOH concentration 1.5%, w/v), 71.53% of lignin removal (6.02% lignin retained in the residue), 78.51% of cellulose release, and 9.99% hemicellulose were obtained. A significant amount of reducing sugars (736 mg/ g of rice straw) was hydrolyzed after bacterial hydrolysis (Bacillus sp. BMP01) of the microwave assisted NaOH pretreated sample. In the case of wheat straw, the pretreatment condition at 1600C, 1.5% NaOH concentration and 15 minutes preserved high cellulose and removed high amount of lignin. At this point 38.34% of hemicellulose and 74.15% of cellulose were preserved in the solid residue and 69.49% of lignin was solubilized. 718 mg/g of reducing sugars was released after hydrolysis pretreated wheat straw by Bacillus sp. BMP01. Ethanol yield of 0.348 g/g of total reducing sugars was obtained after 96 hours of fermentation. This study demonstrated that the combination of microbial hydrolysis and microwave assisted NaOH pretreatment enhanced ethanol yield. Overall, this study demonstrated the possibility of lignocellulose biomass conversion by coupling various pretreatment methods with microbial hydrolysis for enhancing bioethanol yield. Moreover, it demonstrated that the guts of termites comprise of lignocellulose degrading bacteria that can be cultured and grown in a bioreactor and can be used for the production of vital chemicals like bioethanol. This proofs the possibilities of microbial hydrolysis in replacing enzymatic hydrolysis in lignocellulose biomass conversion to bioethanol.

2020-01-01T00:00:00Z