Abstract. Khoirunnisa NS, Anwar S, Santosa DA. 2020. Isolation and selection of cellulolytic bacteria from rice straw for consortium of microbial fuel cell. Biodiversitas 21: 1686-1696. Cellulose such as in rice straw can be utilized as an organic substrate in Microbial Fuel Cell (MFC) to generate electricity by microorganisms as a biocatalyst. This research aimed to get cellulose-degrading bacteria with high capability to degrade rice straw and able to be used as consortium with exoelectrogen bacteria in Microbial Fuel Cell. The stages of research included: (i) isolation of the bacteria using carboxymethylcellulose (CMC) agar medium, (ii) selection of the isolates for that purpose, (iii) enzyme assay and MFC performance test, and (iv) identification of selected isolate. There were 125 isolates that were obtained. Selection based on the ability to degrade cellulose as indicated by clear zone on CMC medium resulted in 23 isolates. Ten isolates belong to anaerobic facultative bacteria were selected. Three of them were synergistic with exoelectrogen bacteria. The three isolates were tested for exoglucanase (Avicel) and total enzyme activity (Filter Paper) with the highest results were 6.21 U/mL (isolate J404) and 5.88 U/mL (isolate J401), respectively. The optimum MFC performance was achieved by one isolate, J401, which produced highest voltage of 40.8 mV and a power density of 0.33 mW/m2. The best isolate, J401, was identified as Xanthomonas translucens based on 16S rRNA method.

Rice straw can be utilized as an organic substrate in Microbial Fuel Cell (MFC) to generate electricity by microbes as a biocatalyst. This research was aimed to observe the effect of Xanthomonas translucens ICBB 9762 inoculation pretreatment on microwave-assisted alkali treated rice straw on the lignocellulosic structure change of rice straw and to observe the performance of MFC system fed by treated rice straw. The stages of research included: (1) pretreatment of rice straw through microwave-assisted alkali and Xanthomonas translucens ICBB 9762 inoculation, (2) observation of MFC performance including electrical voltage; electrical current; power density; and Coulombic efficiency, and (3) anolite analysis including COD removal, pH and Eh. The result showed that rice straw was successfully decomposed by inoculation of Xanthomonas translucens ICBB 9762 on microwave-assisted alkali pretreatment which the highest cellulose yield about 29.36 %. Treated rice straw produced better performance than rice straw without pretreatment which the best performance resulted by the combination of Xanthomonas translucens ICBB 9762 inoculation and microwave-assisted alkali pretreatment which produce electrical voltage, electrical current, and power density value of 337.90 mV, 0.39 mA, and 26.20 mW/m2, respectively. The utilization of solid substrate such as rice straw need more attention due to there was COD enhancement while in COD reduction reach COD removal efficiency and coulombic efficiency ranged 5.15 - 54.08 % and 0.25 - 7.83 %, respectively. HIGHLIGHTS Microbial Fuel Cell fueled by lignocellulose substrate, which is rice straw Lignocellulose structure deconstruction through microwave-assisted alkali pretreatment A combination of microwave-assisted alkali and cellulose-degrading bacteria inoculation pretreatment for rice straw generate the highest electricity Electricity generation improvement in microbial fuel cell through mix culture between cellulose-degrading bacteria and exoelectrogen bacteria Cellulose degrading bacteria increase Chemical Oxygen Demand (COD) due to the solubility of low molecular weight organic compounds increasing during microbial fuel cell incubation