Analysis of Microbial Consortia with High Cellulolytic Activities for Cassava Pulp Degradation

¹ Department of Biology, Faculty of Science, Srinakharinwirot University, Bangkok, Thailand
² Department of Chemical Engineering, Faculty of Engineering, King Mongkut’s University of Technology North Bangkok (KMUTNB), Bangkok, Thailand
³ Department of Chemistry, University of New England, Australia
⁴ Department of Mechanical and Process Engineering, The Sirindhorn International Thai-German Graduate School of Engineering (TGGS), King Mongkut’s University of Technology North Bangkok (KMUTNB), Bangkok, Thailand
⁵ Department of Microbiology, Faculty of Science, Srinakharinwirot University, Bangkok, Thailand

^* Corresponding author: somkiatp@g.swu.ac.th

Abstract

Biogas production is one of the means to manage the cassava pulp waste obtained from the cassava processing plants. The success of the process is determined by the hydrolysis in an anaerobic digester. When the digester failure is found, the new microbial consortium inoculum is introduced to the system with the long period of set up time. This research aimed to construct the endemic microbial consortium by re-cultivating the cellulolytic microbial consortia obtained from cassava pulp and digester wastewater with the expected shorter set up time. Modifications of enrichment and re-cultivation methods by varying the nutrients, pH and temperature improved the enzymatic hydrolysis yields, as reducing sugars, of CMC, rice straw and cassava pulp substrates approximately 9, 3, and 13 times, respectively. To analyze the enzymatic activities of the selected microbial consortia, the cellulase enzyme was extracted, partially purified and analyzed on CMC-zymogram. The ~130 kDa-sized cellulase enzyme was identified with endocellulase activity, and it was considered as a relatively large molecular size molecule compared to most bacterial endocellulases. The selected microbial consortia were tested for their biomass degradation capacities, and the optimal operational condition was obtained at pH 7.0 and 30 °C. This optimal condition showed the proof of the concept that this re-cultivated consortium could be applied in on-site digester with high efficiency.