STUDIES ON MICROBIAL PRODUCTION OF CELLULASES BY FERMENTATION PROCESS

Abstract

Cellulases have a wide range of applications in various process industries. The major application of cellulases are in the biomass conversion industry for bioethanol production. Ethanol produced from renewable resources is being considered globally as the most prominent and possible substitute for fossil fuel. Today the production cost of bioethanol from lignocellulose is still too high. Cellulase production is the most expensive step during ethanol production from cellulosic biomass and it accounted for approximately 40% of the total cost. Therefore efforts are to be intensified to produce ethanol efficiently through improved and cost effective cellulase production technologies. Cellulase also plays a vital and integral role in waste paper recycling. Lignocellulosic biomass is the most abundant solid waste in the world thus it can provide some of the most promising feedstocks for the production of energy, enzymes and chemicals. Most microbial cellulases are inducible enzymes, and like other extracellular enzymes, they are secreted when the microorganisms are grown on cellulose or cellulosic components present in the raw materials. Inducers play a vital role in cellulase biosynthesis by microorganisms.. Three different types of morphology such as filamentous mycelia, pulpy and pelleted forms were observed with T.reesei, N crassa and A. niger fungal strains. 30°C was found most effective temperature with majority of the fungal strains used in growth studies. Maximum growth rate has been observed for Aspergillus strains with glucose (11.26g/L), xylose and maltose(10.68g/L) sugars, whereas Trichoderma strains showed highest growth in glucose(12.88g/L) and closely followed in lactose(10.83g/L) sugar.From the above experimental observation we suggests that sugar uptake capacity was much faster in Neurospora crassa for maltose, sucrose and glucose in comparison to lactose and xylose. Trichoderma ressei (9.88g/L)showed higher growth as well as Aspergillus niger (9.20g/L) exhibited highest growth and growth rate under whey based culture medium.on the other hand Neurospora crassa illustrated least growth and growth rate under such industrial waste containing culture medium. On the other hand it has been observed that growth and growth rate was much better in boiled bagasse containing medium for most of the culture excluding T viride(6.28g/L). The sugars present in these industrial waste were utilized by fungal strains makes the culture development process more cost effective and environment friendly. Significant improvement in the cellulases activities have been achieved with T reesei, N. crassa and A. niger respectively using experimental design or set of combinations of process parameters. It has also been observed that inoculum dosages was the least effective parameters in most of the cases, while temperature was found much effective parameters in most of the cases. Maximum cellulase activity was observed with cellulose sugar while least cellulase activity was observed with arabinose sugar by T.reesei. Higher cellulase activity was observed with meat peptone, proteose peptone and yeast extract for Aspergillus strains while N.crassa showed higher activities with meat extract and proteose peptone.On the other hand higher cellulase activity was observed with Oil of olive and Tween 80 surfactants while least cellulase activity was observed with Triton X-100 and oil of castor. Higher cellulase activity was observed with 30% dosages of whey while increasing the dosages cellulase activity was not significantly increases with T reesei, while N. crassa showed least cellulase activity under whey based medium. Higher cellulase activity was observed with wheat starch hydrolysates mixed with 30% whey based by Trichoderma reesei ,while potato starch hydrolysates was found much effective with N crassa. On the other hand boiled bagasse and bagasse hydrolysates containing medium showed significant activity with T.reesei while wheat straw hydrolysates was found not much effective for most of the strains.Wheat bran bed was found much effective bed material followed by ground nut shell bed. For the effective utilization of few conventional raw materials acid or alkali pretreatment technology have been introduced. Alkali treatment was found much effective in cellulase production with bagasse raw material Mixed raw material strategy has been also used for cellulase production. Improvement in cellulase activities was observed with (B+GSW+WB) combination as compared to bagasse was taken singly. Mixed microbial cultures strategies (Trichoderma and Aspergillus strains) have been used for the production of complete set of cellulases. It was observed that T. reesei and A.niger (1:1) was found much effective combination to produces significantly higher cellulase and cellobiase activity. Higher cellulase activities were observed with proteose peptone and yeast extract for Aspergillus strains while meat extract and proteose peptone were much effective for N.crassa.It has also been observed that higher dosages of nitrogen sources was not much effective in wheat bran and GSW bed as compared to bagasse and wheat straw solid bed. Keeping the view of waste management acid treated egg shell waste has been used as calcium salts in cellulase production. Significant cellulase activity was observed with N.crassa strain having egg shell waste containing media.Higher increment in cellulase activities was observed with wheat starch hydrolysates for T.reesei and A.niger while N.crassa showed significant activity with potato starch hydrolysates.5% dosages of hydrolysates was found much effective for most of the strains. 5% H2SO4 treated wheat straw as well as 10% H2SO4 treated bagasse hydrolysate were found much effective for microbial growth and cellulase production.Cellulase activity was significantly higher for sugarcane bagasse than wheat straw hydrolysates used. Mutagenic agents such as UV and Etbr on microbial cultures growth, sustainability as well as on cellulase production have been investigated. Significant improvement in growth was observed with mutant, while slight improvement in cellulase activities were also observed. Unconventional and novel raw materials such as pea peel waste and others peel wastes have been used in solid. state fermentative production for making cost effective and efficient approach. It has been observed from the experimental results that Trichoderma strains produces significant cellulase activity (2.86IU/mL) with non conventional raw materials such as pea peel waste.It was observed that incorporation of whey and starch hydrolysates significantly enhances the cellulase activities with T.reesei compared to other strains.Luffa cylindrica peel bed was found quite effective raw materials as compared to others. Cellulase production by Aspergillus niger strain using surface adheshion fermentation (biofilm fermentation) was investigated. Significant improvement in the cellulases were observed with muslin cloth with 3 hole and polyester sheet based biofilm fermentation as compared to liquid state fermentation without solid support. It has been also observed that cellulases from T viridae was found better strains for the enzymatic deinking with their better treated handsheet properties in terms of brightness and tensile strength as compared to chemically deinked pulp.