Thermostable Xylanase Production by Geobacillus sp. Strain DUSELR13, and Its Application in Ethanol Production with Lignocellulosic Biomass

Abstract

The aim of the current study was to optimize the production of xylanase, and its application for ethanol production using the lignocellulosic biomass. A highly thermostable crude xylanase was obtained from the Geobacillus sp. strain DUSELR13 isolated from the deep biosphere of Homestake gold mine, Lead, SD. Geobacillus sp. strain DUSELR13 produced 6 U/mL of the xylanase with the beechwood xylan. The xylanase production was improved following the optimization studies, with one factor at a time approach, from 6 U/mL to 19.8 U/mL with xylan. The statistical optimization with response surface methodology further increased the production to 31 U/mL. The characterization studies revealed that the crude xylanase complex had an optimum pH of 7.0, with a broad pH range of 5.0–9.0, and an optimum temperature of 75 °C. The ~45 kDa xylanase protein was highly thermostable with t1/2 of 48, 38, and 13 days at 50, 60, and 70 °C, respectively. The xylanase activity increased with the addition of Cu+2, Zn+2, K+, and Fe+2 at 1 mM concentration, and Ca+2, Zn+2, Mg+2, and Na+ at 10 mM concentration. The comparative analysis of the crude xylanase against its commercial counterpart Novozymes Cellic HTec and Dupont, Accellerase XY, showed that it performed better at higher temperature, hydrolyzing 65.4% of the beechwood at 75 °C. The DUSEL R13 showed the mettle to hydrolyze, and utilize the pretreated, and untreated lignocellulosic biomass: prairie cord grass (PCG), and corn stover (CS) as the substrate, and gave a maximum yield of 20.5 U/mL with the untreated PCG. When grown in co-culture with Geobacillus thermoglucosidasius, it produced 3.53 and 3.72 g/L ethanol, respectively with PCG, and CS. With these characteristics the xylanase under study could be an industrial success for the high temperature bioprocesses.

A detailed overview of xylanases: an emerging biomolecule for current and future prospective

“…The requirement of these nitrogen sources varies for different microorganisms; therefore, optimizing the type and level of nitrogen source in the media is an important parameter (Seyis and Aksoz 2005;Naveen et al 2014;Irfan et al 2016). Trace elements, amino acids, and vitamins are also important parameters for the growth of different microorganisms (Simair et al 2010;Bibra et al 2018). Therefore, regulating their levels in the media is important for regulating the production of xylanase.…”

“…These strategies resulted in an enhancement in reaction rates and ethanol yields (Eklund and Zacchi 1995;Sun and Cheng 2002). Bibra et al (2018) showed thermostable xylanase production using Geobacillus sp. DUSELR13, which is applied further for ethanol generation from LCB.…”

Parageobacillus thermantarcticus, an Antarctic Cell Factory: From Crop Residue Valorization by Green Chemistry to Astrobiology Studies

“…WSUCEF1 isolated from soil and Geobacillus sp. DUSELR 13 isolated from the deep gold mines of South Dakota [49,50]. Xylanase from Geobacillus sp.…”

“…WSUCEF1 showed a half-life of 18 days and 12 days at 60 • C and 70 • C, respectively, while Geobacillus sp. DUSELR 13 produced 31 U/mL after optimization and exhibited a half-life of 13 days at 60 • C and 70 • C [49,50].…”

“…The optimization of enzymatic procedures for the conversion of waste lignocellulosic materials in XOS molecules using the xylanolytic enzymatic set from Geobacillus microorganisms produced extremely interesting results and was recently reported [50,51,98].…”