Synthesis of Biopolymers from a Geobacillus sp. WSUCF1 Using Unprocessed Corn Stover
2020
Wang, Jia | Salem, David R. | Sani, Rajesh K.
A lignocellulolytic and thermophilic bacterium Geobacillus sp. WSUCF1 was investigated for its production of biopolymers (exopolysaccharides, EPSs) using agricultural waste corn stover. The maximum EPS production achieved was 410 mg/L in a 40-L bioreactor. Four purified EPSs were obtained: the two neutral EPSs were glucomannan and the two negatively charged EPSs were mannan. The molecular weight of all four EPSs was estimated to be approximately 1000 kDa, and their FTIR and NMR spectra indicated that they were mainly composed of an α-type glycosidic bond in a linear structure. The mannan EPSs had a low level of crystallinity and displayed high thermal stability, with thermal degradation temperatures of 309 and 316 °C, while the glucomannan EPSs were essentially amorphous and had moderate thermal stability, with thermal degradation temperatures of 203 and 227 °C. A mannan EPS (EPS 1–2) showed exceptional biocompatibility, with a noncytotoxic concentration as high as 4000 μg/mL using HEK-293 cell line. The green metrics showed that EPS production using corn stover appears to be more sustainable than using glucose. This study reports for the first time a cultivation strategy for EPS production by a lignocellulolytic thermophile using corn stover as a carbon source, requiring no biomass pretreatment.
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