(400-49) Targeted enzymatic degradation of the pectic glycan Rhamnogalacturonan I (RG-I) to enhance solubilization of poplar biomass during consolidated bioprocessing
Graduate Research Assistant University of Georgia Athens, Georgia
Body of Abstract: Plant biomass is a renewable carbon feedstock for biofuel production. Consolidated bioprocessing (CBP) by Clostridium thermocellum offers a single step microbial platform for simultaneous solubilization of biomass and conversion to biofuels. Recently it was shown that the cell wall pectic polysaccharide rhamnogalacturonan-I (RG-I) is not effectively solubilized by C. thermocellum during CBP [1] and that RG-I is a determinant in cell-cell adhesion in woody plants [2,3]. We hypothesize that introduction of RG-I-degrading enzymes during CBP may enhance solubilization of poplar biomass by C. thermocellum. To test this hypothesis, we searched the genome of C. thermocellum for genes encoding predicted RG-I degrading enzymes and evaluated their expression during the fermentation process. Bioinformatic and transcriptomic data revealed that although C. thermocellum encodes putative RG-I acetyl esterase and RG-I lyase, their level of expression is low during CBP. RG-I side-chain-targeting arabinase, arabinosidase, galactanase and galactosidase also appear to exist in the C. thermocellum genome, but not RG-I endohydrolase, rhamnosidase and galacturonidase. To determine if CBP can be improved by augmentation with RG-I degrading enzymes, 22 potential RG-I degradative enzymes comprising six from C. thermocellum and 16 from other thermophiles have been identified and are being heterologously expressed and analyzed for enzyme activity.
References
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2. Yang et al. 2020. Plant Biotechnology Journal 18: 1027–1040.
3. Liu et al. 2022. Industrial crops and products, 184: 115054.