WHOLE-CELL CATALYSED BIOTRANSFORMATION OF 5-HMF TO FURANIC CARBOXYLIC ACIDS USING LENTIBACILLUS SALARIUS BPIITR

Abstract

5-hydroxymethyl furfural (5-HmF) is a platform chemical derived from hexose sugar dehydration process. Current lignocellulosic biomass abundance and their sugar portion holds a great potential in synthesis of 5-HmF, however, being toxic component to humans and ecology, its need of the hour to identify the strategies to transform to value added products. Although, chemical routes have been widely explored to valorise these toxic components, biological methods hold a great potential in selectively synthesis bio-based chemicals. Furan carboxylic acids are one such chemical, they have been considered as alternative to various petrochemical derived plastics. In current research, efforts have been made to explore the production of furan derived mono- and di-carboxylic acids using whole cells of halophilic bacterium Lentibacillus salarius BPIITR. Initially, different substrates were screened to assess the oxidase enzyme involved in biotransformation of 5-HmF. Among the studied substrates, 4-methoxy benzyl alcohol oxidation was found to be profound in whole cells i.e., 617.1 ± 39.45 U mg-1 dry cell weight. In synthetic sugar fed medium the highest biomass growth was observed in fructose (3.47 ± 0.04 mg mL-1), followed by glucose (2.86 ± 0.15 mg mL-1) and xylose (2.18 ± 0.03 mg mL-1). However, the oxidase activity found significantly less compared to lignocellulosic biomass hydrolysate. For instance, the highest activity observed in synthetic sugar was 221.54 ± 34.26 U mg-1 dcw, whereas in delignified bagasse hydrolysate grown cells exhibited activity up to 546. 94 ± 15.23 U mg-1 dcw. Furthermore, influence of pH, temperature, and hydrogen peroxide on residual activities of whole cell was explore. The residual activity significantly decreased below 50 % at above temperature of 50 °C, whereas between pH 6.0 - 8.0, the residual activity remaining was above 85 %. In addition, up to 20 mM hydrogen peroxide concentration, the residual activity retained was above 50 %.