Identification of Cellulose-Degrading Bacteria and Assessment of Their Potential Value for the Production of Bioethanol from Coconut Oil Cake Waste.

Bioconversion of lignocellulosic biomass is a highly promising alternative to rapidly reduce reliance on fossil fuels and greenhouse gas emissions. However, the use of lignocellulosic biomass is limited by the challenges of efficient degradation strategies. Given this need, Bacillus tropicus (B. tropicus) with cellulose degradation ability was isolated and screened from rotten dahlia. The strain efficiently utilized coconut oil cake (COC) to secrete 167.3 U/mL of cellulase activity. Electron microscopy results showed significant changes in the structure and properties of cellulose after treatment with B. tropicus, which increased the surface accessibility and the efficiency of the hydrolysis process. The functional group modification observed by Fourier transform infrared spectroscopy indicated the successful depolymerization of COC. The X-ray diffraction pattern showed that the crystallinity index increased from 44.8% to 48.2% due to the hydrolysis of the amorphous region in COC. The results of colorimetry also reveal an efficient hydrolysis process. A co-culture of B. tropicus and Saccharomyces cerevisiae was used to produce ethanol from COC waste, and the maximum ethanol yield was 4.2 g/L. The results of this work show that B. tropicus can be used to prepare biotechnology value-added products such as biofuels from lignocellulosic biomass, suggesting promising utility in biotechnology applications.

Screening of cellulose-degrading yeast and evaluation of its potential for degradation of coconut oil cake.

Coconut oil cake (COC), a byproduct of oil extraction, contains high levels of cellulose. The aim of this study was to isolate a cellulose-degrading yeast from rotten dahlia that can effectively use COC as the only carbon source for cellulase secretion. Based on screening, Meyerozyma guillermondii CBS 2030 (M. guillermondii) was identified as a potential candidate, with the highest cellulolytic activity among the yeast strains isolated, with the carboxymethyl cellulase (CMCase) activity reaching 102.96 U/mL on day 5. The cellulose in COC samples was evaluated before and after degradation by M. guillermondii. Analysis based on field emission scanning electron microscopy (FESEM) revealed that the COC structure was changed significantly during the treatment, indicating effective hydrolysis. Fourier transform infrared spectroscopy (FTIR) of the modified functional groups indicated successful depolymerization of coconut cake. X-ray diffraction (XRD) and analysis of color differences established effective degradation of COC by M. guillermondii. The results demonstrate that M. guillermondii effectively secretes CMCase and degrades cellulose, which has important practical significance in COC degradation.