Statistical optimization of saccharificaion of carbohydrate content of alkali pretreated sugarcane bagasse by enzyme cocktail produced by Bacillus vallismortis MH 1 and Bacillus aestuarii UE25

Abstract

Saccharification of widely available agro-industrial waste product, sugarcane bagasse (SB) can be achieved by microbial enzymes. Since single enzyme cannot completely saccharify SB, therefore, enzyme cocktails are designed for effective saccharification. In this study, alkali (NaOH) pretreated SB was saccharified using enzyme preparations from a halotolerant bacterium, Bacillus vallismortis MH 1 and a thermophilic bacterium, B. aestuarii UE25. The factors affecting the process of saccharification were statistically optimized by Central Composite design (CCD). After analysis, CCD predicted the optimum conditions i.e. 8.08 U of B. vallismortis MH 1 and 1.92 U of B. aestuarii UE25 for 1 g of substrate; temperature, 65℃; pH, 4; and reaction time, 48 h. Under optimal conditions, 501 mg g−1 reducing sugars were obtained after the saccharification of pretreated SB. The structural analysis of substrate by scanning electron microscopy, Fourier transform infrared spectroscopy and gravimetric analysis showed damaged structure, increased porosity and a reduction in cellulosic content, indicating significant degradation of the SB by the enzyme cocktail. Hence, it can be concluded that enzyme cocktail used in this study is effective for the saccharification of alkali pretreated SB.

Keywords

• Alkali pretreatment
• Bacillus aestuarii UE25
• Bacillus vallismortis MH 1
• Central Composite design
• saccharification
• sugarcane bagasse