Mixed Lignocellulosic Biomass Degradation and Utilization for Bacterial Cellulase Production

Abstract

Feedstock supply challenges provide impetus into the exploration of lignocellulosic mixtures in bioprocessing. Such mixtures have not been fully explored for bacterial cellulase production. Four bacterial species were evaluated for ability to utilize a mixture of oil palm and rice residues (MS) for cellulase production. Bacillus aerius, Bacillus anthracis, Cellvibrio japonicus and Klebsiella pneumoniae with ability to utilize MS for growth were investigated. A two-step sequential strategy was employed in selecting the candidate for cellulase production and degradation of MS. B. aerius displayed better cellulolytic ability than the others during plate screening on carboxymethyl cellulose-enriched medium. However, C. japonicus produced the highest activities of endoglucanase and total cellulase during targeted screening on MS. Analyses revealed that sequential pretreatment with NaOH and moist heat increased the accessibility and disrupted the surface morphology of MS for subsequent bacterial utilisation. C. japonicus achieved significant degradation of MS with 52.33 % substrate dry weight loss after 7 days as compared to B. aerius which degraded 21.33 % of MS in the same period. Substrate was hydrolyzed via the amorphous region. The low residual concentration of reducing sugars in the medium suggested that C. japonicus converted the liberated sugars into other products.