Synthesis of Biopolymers from a Geobacillus sp. WSUCF1 Using Unprocessed Corn Stover

Abstract

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.

Thermophilic Exopolysaccharide Films: A Potential Device for Local Antibiotic Delivery

“…The Geobacillus sp. strain WSUCF1 media was prepared in a 1000 mL flask containing 6 g of shredded corn stover, 20 g yeast extract, 3 g NaCl, and 1000 mL of distilled (DI) water [ 9 ]. The corn stover, yeast extract, and NaCl solution was first made homogeneous using a magnetic stir bar with the pH set to 7.0, then allowed to autoclave at 121 °C for 20 min.…”

“…To precipitate the crude EPS, a 1:1 ratio of absolute ethanol was added to the remaining supernatant and allowed to sit in a freezer overnight at −20 °C. Lastly, the crude EPS was obtained by centrifuging the ethanol/supernatant solution at 8000× g for 40 min [ 9 ]. Following collection, the crude EPS was stored at −20 °C without a cryoprotectant.…”

“…Geobacillus sp. WSUCF1 is capable of consuming lignocellulosic biomass to produce EPSs without the need for pretreatment [ 9 ].…”

Comparative Highly Efficient Production of β-glucan by Lasiodiplodia theobromae CCT 3966 and Its Multiscale Characterization

“…Cunha et al [11] determined yeast extract (2 g/L) as the best nitrogen source, between organic and inorganic, and reported 2.46 g/L of lasiodiplodan. Naturally, RBE and SBE are complex nitrogen sources, similar to yeast extract, i.e., carbon, sulfur, protein, amino acids, minerals, vitamins, and other essential growth factors for various microorganisms [28,29]. Alternatively, the VMSM control experiment resulted in 5.21 g/L of lasiodiplodan and 7.97 g/L of fungal biomass.…”

“…The biopolymer purity is essential, to know the total sugar content, and the presence of impurities, i.e., proteins, lipids, aromatics, nucleic acids, minerals, etc., [29]. Table 2 summarizes the physicochemical properties found for lasiodiplodan samples.…”