Coordination of consolidated bioprocessing technology and carbon dioxide fixation to produce malic acid directly from plant biomass in Myceliophthora thermophila

Jingen Li,Bingchen Chen,Shuying Gu,Yongli Zhang,Tao Sun,Chaoguang Tian,Taju Wu,Wenliang Sun,Zhen Zhao,Qian Liu,Defei Liu

doi:10.1186/s13068-021-02042-5

Abstract

BackgroundConsolidated bioprocessing (CBP) technique is a promising strategy for biorefinery construction, producing bulk chemicals directly from plant biomass without extra hydrolysis steps. Fixing and channeling CO2 into carbon metabolism for increased carbon efficiency in producing value-added compounds is another strategy for cost-effective bio-manufacturing. It has not been reported whether these two strategies can be combined in one microbial platform.ResultsIn this study, using the cellulolytic thermophilic fungus Myceliophthora thermophila, we designed and constructed a novel biorefinery system DMCC (Direct microbial conversion of biomass with CO2 fixation) through incorporating two CO2 fixation modules, PYC module and Calvin–Benson–Bassham (CBB) pathway. Harboring the both modules, the average rate of fixing and channeling 13CO2 into malic acid in strain CP51 achieved 44.4, 90.7, and 80.7 mg/L/h, on xylose, glucose, and cellulose, respectively. The corresponding titers of malic acid were up to 42.1, 70.4, and 70.1 g/L, respectively, representing the increases of 40%, 10%, and 7%, respectively, compared to the parental strain possessing only PYC module. The DMCC system was further improved by enhancing the pentose uptake ability. Using raw plant biomass as the feedstock, yield of malic acid produced by the DMCC system was up to 0.53 g/g, with 13C content of 0.44 mol/mol malic acid, suggesting DMCC system can produce 1 t of malic acid from 1.89 t of biomass and fix 0.14 t CO2 accordingly.ConclusionsThis study designed and constructed a novel biorefinery system named DMCC, which can convert raw plant biomass and CO2 into organic acid efficiently, presenting a promising strategy for cost-effective production of value-added compounds in biorefinery. The DMCC system is one of great options for realization of carbon neutral economy.

Highlights

Consolidated bioprocessing (CBP) technique is a promising strategy for biorefinery construction, producing bulk chemicals directly from plant biomass without extra hydrolysis steps
Heterologous expression of genes encoding CBB cycle enzymes in M. thermophila Previously, we performed metabolic modification in M. thermophila to generate strain JG207, which can produce malic acid using plant lignocellulose as the carbon source [9]
Xylose and arabinose are metabolized by pentose phosphate pathway, which can provide the substrate for PRK of the CBB cycle

Summary

Introduction

Consolidated bioprocessing (CBP) technique is a promising strategy for biorefinery construction, producing bulk chemicals directly from plant biomass without extra hydrolysis steps. Consolidated bioprocessing (CBP), featuring the hydrolysis and fermentation in a single process step without adding any extra cellulases, is widely recognized as a promising strategy for cost-effective production of plant biomass-derived biofuels and chemicals [5]. CBP entails microbial engineering by functional expression of cellulases in a fermentative organism, or incorporation of the desired product-synthesis pathway into a cellulase-producing organism [3, 6] Cellulolytic organisms, such as Trichoderma [7], Aspergillus, Clostridium [8], and Myceliophthora [9, 10] have been tried as CBP strains for direct conversion of plant cell wall materials into biofuels and biochemicals, including ethanol [11], isobutanol [12], itaconic acid [13], and malic acid [9, 10]

Methods

Results

Discussion

Conclusion