Conversion of cellulose and hemicellulose of biomass simultaneously to acetoin by thermophilic simultaneous saccharification and fermentation

Abstract

BackgroundAcetoin (3-hydroxy-2-butanone), the precursor of biofuel 2,3-butanediol, is an important bio-based platform chemical with wide applications. Fermenting the low-cost and renewable plant biomass is undoubtedly a promising strategy for acetoin production. Isothermal simultaneous saccharification and fermentation (SSF) is regarded as an efficient method for bioconversion of lignocellulosic biomass, in which the temperature optima fitting for both lignocellulose-degrading enzymes and microbial strains.ResultsA thermotolerant (up to 52 °C) acetoin producer Bacillus subtilis IPE5-4 which simultaneously consumed glucose and xylose was isolated and identified. By compound mutagenesis, the mutant IPE5-4-UD-4 with higher acetoin productivity was selected. When fermenting at 50 °C in a 5-L bioreactor using glucose as the feedstock by strain IPE5-4-UD-4, the acetoin concentration reached 28.83 ± 0.91 g L−1 with the acetoin yield and productivity of 0.34 g g−1 glucose and 0.60 g L−1 h−1, respectively. Furthermore, an optimized and thermophilic SSF process operating at 50 °C was conducted for acetoin production from alkali-pretreated corncob (APC). An acetoin concentration of 12.55 ± 0.28 g L−1 was achieved by strain IPE5-4-UD-4 in shake flask SSF, with the acetoin yield and productivity of 0.25 g g−1 APC and 0.17 g L−1 h−1. Meanwhile, the utilization of cellulose and hemicellulose in the SSF approach reached 96.34 and 93.29%, respectively. When further fermented at 50 °C in a 5-L bioreactor, the concentration of acetoin reached the maximum of 22.76 ± 1.16 g L−1, with the acetoin yield and productivity reaching, respectively, 0.46 g g−1 APC and 0.38 g L−1 h−1. This was by far the highest acetoin yield in SSF from lignocellulosic biomass.ConclusionsThis thermophilic SSF process provided an efficient and economical route for acetoin production from lignocellulosic biomass at ideal temperature for both enzymatic hydrolysis and microbial fermentation.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-017-0924-8) contains supplementary material, which is available to authorized users.

Pretreatment Ethanol From Cellulosic

“…The hemicellulose and cellulose polymers are hydrolyzed with enzymes or acids to release monomeric sugars. The sugars from the pretreatment and enzymatic hydrolysis steps are fermented by bacteria, yeast or filamentous fungi, although the enzymatic hydrolysis and fermentation can also be performed in a combined step -a so-called simultaneous saccharification and fermentation (SSF) [14]. Fig.…”

Synergism of microorganisms and enzymes in solid-state fermentation of animal feed. A review

“…xylanase (Chu et al, 2017) Palm kernel (Trachycarpus fortunei) cake Lactobacillus plantarum (Lee et al, 2019), Paenibacillus curdlanolyticus (Alshelmani et al, 2014) hemicellulase (xylanase, mannanase), cellulase, proteolytic (endoprotease) (Lee et al, 2019;Olukomaiya et al, 2019) Peas (Pisum sativum L.) Bacillus subtilis, Bacillus licheniformis (Goodarzi Boroojeni et al, 2017; α-glucosidase, protease, pectinase (Goodarzi Boroojeni et al, 2017; Barley (Hordeum vulgare L.) Lactobacillus plantarum, Rhizopus oryzae (Wang et al, 2019), lacto-acid bacteria (Yasar and Tosun, 2018) glucoamylase (Wang et al, 2019), cellulose (Yasar and Tosun, 2018) Grain (Olyza sativa L.) by-product Pediococcus acidilactici (Bartkiene et al, 2018) xylanase, cellulase, β-glucanase (Bartkiene et al, 2018) Potatoes (Solanum tuberosum L.) Lactobacillus plantarum (Du et al, 2018) cellulose (Du et al, 2018) Maize (Zea mays L.) stalk Chaetomium, white-rot fungi, Lactobacillus plantarum (Atuhaire et al, 2016), Bacillus licheniformis (Alokika and Singh, 2019) cellulase, xylanase (Alokika and Singh, 2019) Maize (Zea mays L.) cob Bacillus subtilis (Jia et al, 2017), Bacillus licheniformis, Lactobacillus plantarum, Saccharomyces cerevisiae (Alokika and Singh, 2019) xylanase (Alokika and Singh, 2019), cellulase, hydrolysis enzyme (Jia et al, 2017) Alfalfa (Medicago sativa L.) Lactobacillus plantarum, Pediococcus pentosaceus (Chen et al, 2019), yeast, lacto-acid bacteria (Ding et al, 2013), Lactobacillus buchneri (Kung et al, 2003) cellulase, hemicellulose (Chen et al, 2019), viscozyme (Schmidt et al, 2001), plant enzyme (Ding et al, 2013), β-glucanase, α-amylase, xylanase, and galactomannase (Kung et al, 2003) Blood meal Bacillus subtilis…”

Engineering central pathways for industrial-level (3R)-acetoin biosynthesis in Corynebacterium glutamicum

“…Therefore, the toxicity of the very high acetoin concentrations will no doubt prevent glucose assimilation and acetoin production of CGS11, and even activate its underlying acetoin catabolism. Since acetoin metabolism is complex and still not clearly elucidated, several successful strategies, such as physical/ chemical mutagenesis [54], adaptive evolution [52,53] or omics focusing on global transcriptional/metabolism level responses to acetoin stress [55], could be adopted to deeply understand and improve the acetoin tolerance of C. glutamicum in future studies.…”