Use of thermophilic bacteria to utilize sugarcane bagasse: Efficient cellulase production, saccharification, and hydrolysate applications

Sugarcane bagasse (SB) a renewable and abundant source of rich fermentable sugars has been reported extensively to produce microbial enzymes and other valuable products. However, most of the SB-based processes require its pretreatment which is an additional step incurring time and cost. In this study, fermentation of SB by bacterial strains without any pretreatment was carried out to obtain crude cellulase preparation. Enzyme mediated saccharification of SB was carried out and the hydrolysate was analyzed for the presence of reducing sugars and free radical scavenging activity. It was found that 65.86, 42.03 and 88.8 IU mL^-1 endoglucanase was produced by <i>Brevibacillus borstelensis</i> UE10, <i>Neobacillus sedimentimangrovi</i> UE25 and <i>B. borstelensis</i> UE27, respectively by fermenting SB. Crude cellulase preparation of UE10, UE25, and UE27 was used to saccharify SB which resulted in 1.14, 1.47, and 1.58 mg mL^-1 reducing sugars and 1.08, 0.57, and 1.5 mg mL^-1 glucose, respectively. Moreover, the hydrolysate also had radical scavenging activity indicating about its possible application in animal feed. The maximum (35.71 %) amount of bioethanol was produced when UE25 fermented the hydrolysate of SB. The strains UE10 and UE27 produced 31.16 and 27.77 % bioethanol, respectively. Furthermore, Fourier transform infrared spectroscopy, scanning electron microscopy and gravimetric analysis showed the impact of cellulase on structure of SB. Hence, this work expands the understanding of the potential of thermophilic bacterial strains to utilize agricultural waste for the synthesis of valuable products.