Biodelignification and hydrolysis of rice straw by novel bacteria isolated from wood feeding termite

Abstract

In this study, two bacterial strains capable of degrading lignin, cellulose, and hemicellulose were isolated from wood feeding termite. The isolates were identified by 16S rRNA gene sequencing. A bacterium Ochrobactrum oryzae BMP03 capable of degrading lignin was isolated on alkali lignin medium and Bacillus sp. BMP01 strain capable of degrading cellulose and hemicellulose were isolated on carboxymethyl cellulose and xylan media. The efficiency of bacterial degradation was studied by evaluating the composition of rice straw both before and after degradation. The appearance of new cellulose bands at 1382, 1276, 1200, and 871 cm −1 , and the absence of former lignin bands at 1726, 1307, and 1246 cm −1 was observed after biodelignification. This was further confirmed by the formation of channeling and layering of the microstructure of biodelignified rice straw observed under electron microscope. Maximum lignin removal was achieved in separate biodelignification and hydrolysis process after the 14th day of treatment by Ochrobactrum oryzae BMP03 (53.74% lignin removal). Hydrolysis of the biodelignified rice straw released 69.96% of total reducing sugars after the 14th day hydrolysis by Bacillus sp. BMP01. In simultaneous delignification and hydrolysis process, about 58.67% of total reducing sugars were obtained after the 13th day of biotreatment. Separate delignification and hydrolysis process were found to be effective in lignin removal and sugar released than the simultaneous process. The bacteria, Bacillus sp. BMP01, has the ability to degrade hemicellulose and cellulose simultaneously. Overall, these results demonstrate that the possibility of rice straw bioconversion into reducing sugars by bacteria from termite gut.

Mapping the diversity of microbial lignin catabolism: experiences from the eLignin database

“…The lignin barrier is overcome by the termites by a symbiotic relationship with a diverse microbial community, e.g., by exosymbiotic fungi and endosymbiotic gut flora (Maurice and Erdei 2018 ). Examples of aromatic degrading bacteria isolated from the gut flora include Proteobacteria (Harazono et al 2003 ; Kuhnigk and Konig 1997 ; Suman et al 2016 ; Tsegaye et al 2018 ; Van Dexter and Boopathy 2018 ), Actinobacteria (Chung et al 1994 ; Kuhnigk and Konig 1997 ; Watanabe et al 2003 ), and Firmicutes (Kuhnigk and Konig 1997 ), as well as the only Spirochaetes entry in the database (Lucey and Leadbetter 2014 ). Another enrichment reported in Table 4 for bacteria is the isolates from different man-made environments.…”

Towards Sustainable Energy: The Requisite Role of Microorganisms in the Production of Biogas and Bioethanol

“…Therefore, the breakdown of lignin is very essential in gaining access to the full carbohydrate in efficient bioethanol production [75,76]. The bacterium Ochrobactrumoryzae degrades lignin to release cellulose and hemicellulose [77]. Data from studies have also reported that microbes such as Nocardia,…”

“…Rhodococcus, Athrobacter, Streptomyces and Thermomospora spp. are capable of Lignin degradation [77]. However, white-rot fungi are the most efficient members of microorganisms in degrading lignin with notable species including Lentinulaedodes, Phlebia radiate, Ganodermaspp.…”

“…A. niger also produces cellulase enzyme which makes them a better candidate in the hydrolysis of cellulose and hemicellulose [67]. Cellulose degrading bacteria, Serratia marcesceens and Bacillus cereus, have been isolated from wood feeding termites [77].…”

Alkali delignification and Bacillus sp. BMP01 hydrolysis of rice straw for enhancing biofuel yields

“…It can also remove lignin and hemicellulose to a certain extent, which increases the porosity and concentration of amorphous cellulose (Ravindran and Jaiswal 2016;Gao et al 2017;Sun and Cheng 2002;Tsegaye et al 2019a;Tsegaye et al 2019d). These are achieved by different mechanisms such as by applying high pressure and/or temperature, treatment with corrosive chemicals such as acids and alkali, use of enzyme and/or microorganisms, or the use of molecular disruption techniques such as ultrasound and plasma (Ravindran and Jaiswal 2016;Gao et al 2017;Sun and Cheng 2002;Tsegaye et al 2018).…”