Development of the bioeconomy is driven by our ability to access the energy‐rich carbon trapped in recalcitrant plant materials. Current strategies to release this carbon rely on expensive enzyme cocktails and physicochemical pretreatment, producing inhibitory compounds that hinder subsequent microbial bioproduction. Anaerobic fungi are an appealing solution as they hydrolyze crude, untreated biomass at ambient conditions into sugars that can be converted into value‐added products by partner organisms. However, some carbon is lost to anaerobic fungal fermentation products. To improve efficiency and recapture this lost carbon, we built a two‐stage bioprocessing system pairing the anaerobic fungus
The extreme thermophile
- NSF-PAR ID:
- 10102311
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Biotechnology and Bioengineering
- Volume:
- 116
- Issue:
- 8
- ISSN:
- 0006-3592
- Page Range / eLocation ID:
- p. 1901-1908
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
Abstract Piromyces indianae with the yeastKluyveromyces marxianus , which grows on a wide range of sugars and fermentation products. In doing so we produce fine and commodity chemicals directly from untreated lignocellulose.P .indianae efficiently hydrolyzed substrates such as corn stover and poplar to generate sugars, fermentation acids, and ethanol, whichK .marxianus consumed while producing 2.4 g/L ethyl acetate. An engineered strain ofK .marxianus was also able to produce 550 mg/L 2‐phenylethanol and 150 mg/L isoamyl alcohol fromP .indianae hydrolyzed lignocellulosic biomass. Despite the use of crude untreated plant material, production yields were comparable to optimized rich yeast media due to the use of all available carbon including organic acids, which formed up to 97% of free carbon in the fungal hydrolysate. This work demonstrates that anaerobic fungal pretreatment of lignocellulose can sustain the production of fine chemicals at high efficiency by partnering organisms with broad substrate versatility. -
Abstract The production of volatile industrial chemicals utilizing metabolically engineered extreme thermophiles offers the potential for processes with simultaneous fermentation and product separation. An excellent target chemical for such a process is acetone (
T b = 56°C), ideally produced from lignocellulosic biomass.Caldicellulosiruptor bescii (T opt78°C), an extremely thermophilic fermentative bacterium naturally capable of deconstructing and fermenting lignocellulose, was metabolically engineered to produce acetone. When the acetone pathway construct was integrated into a parent strain containing the bifunctional alcohol dehydrogenase fromClostridium thermocellum , acetone was produced at 9.1 mM (0.53 g/L), in addition to minimal ethanol 3.3 mM (0.15 g/L), along with net acetate consumption. This demonstrates thatC. bescii can be engineered with balanced pathways in which renewable carbohydrate sources are converted to useful metabolites, primarily acetone and H2, without net production of its native fermentation products, acetate and lactate. -
Abstract The conversion of lignocellulose‐rich biomass to bio‐based chemicals and higher order fuels remains a grand challenge, as single‐microbe approaches often cannot drive both deconstruction and chemical production steps. In contrast, consortia based bioprocessing leverages the strengths of different microbes to distribute metabolic loads and achieve process synergy, product diversity, and bolster yields. Here, we describe a biphasic fermentation scheme that combines the lignocellulolytic action of anaerobic fungi isolated from large herbivores with domesticated microbes for bioproduction. When grown in batch culture, anaerobic fungi release excess sugars from both cellulose and crude biomass due to a wealth of highly expressed carbohydrate active enzymes (CAZymes), converting as much as 49% of cellulose to free glucose. This sugar‐rich hydrolysate readily supports growth of
Saccharomyces cerevisiae , which can be engineered to produce a range of value‐added chemicals. Further, construction of metabolic pathways from transcriptomic data reveals that anaerobic fungi do not catabolize all sugars that their enzymes hydrolyze from biomass, leaving other carbohydrates such as galactose, arabinose, and mannose available as nutritional links to other microbes in their consortium. Although basal expression of CAZymes in anaerobic fungi is high, it is drastically amplified by cellobiose breakout products encountered during biomass hydrolysis. Overall, these results suggest that anaerobic fungi provide a nutritional benefit to the rumen microbiome, which can be harnessed to design synthetic microbial communities that compartmentalize biomass degradation and bioproduct formation. -
null (Ed.)Biomass conversion to alcohols using supercritical methanol depolymerization and hydrodeoxygenation (SCM-DHO) with CuMgAl mixed metal oxide is a promising process for biofuel production. We demonstrate how maple wood can be converted at high weight loadings and product concentrations in a batch and a semi-continuous reactor to a mixture of C 2 –C 10 linear and cyclic alcohols. Maple wood was solubilized semi-continuously in supercritical methanol and then converted to a mixture of C 2 –C 9 alcohols and aromatics over a packed bed of CuMgAlO x catalyst. Up to 95 wt% of maple wood can be solubilized in the methanol by using four temperature holds at 190, 230, 300, and 330 °C. Lignin was solubilized at 190 and 230 °C to a mixture of monomers, dimers, and trimers while hemicellulose and cellulose solubilized at 300 and 330 °C to a mixture of oligomeric sugars and liquefaction products. The hemicellulose, cellulose, and lignin were converted to C 2 –C 10 alcohol fuel precursors over a packed bed of CuMgAlO x catalyst with 70–80% carbon yield of the entire maple wood. The methanol reforming activity of the catalyst decreased by 25% over four beds of biomass, which corresponds to 5 turnovers for the catalyst, but was regenerable after calcination and reduction. In batch reactions, maple wood was converted at 10 wt% in methanol with 93% carbon yield to liquid products. The product concentration can be increased to 20 wt% by partially replacing the methanol with liquid products. The yield of alcohols in the semi-continuous reactor was approximately 30% lower than in batch reactions likely due to degradation of lignin and cellulose during solubilization. These results show that solubilization of whole biomass can be separated from catalytic conversion of the intermediates while still achieving a high yield of products. However, close contact of the catalyst and the biomass during solubilization is critical to achieve the highest yields and concentration of products.more » « less
-
The presence of lignocellulose-derived microbial inhibitory compounds (LDMICs) in lignocellulosic biomass (LB) hydrolysates is a barrier to efficient conversion of LB hydrolysates to fuels and chemicals by fermenting microorganisms. Results from this study provide convincing evidence regarding the effectiveness of metabolically engineered C. beijerinckii NCIMB 8052 for the fermentation of LB-derived hydrolysates to acetone–butanol–ethanol (ABE). The engineered microbial strain ( C. beijerinckii _SDR) was produced by the integration of an additional copy of a short-chain dehydrogenase/reductase (SDR) gene ( Cbei_ 3904) into the chromosome of C. beijerinckii NCIMB 8052 wildtype, where it is controlled by the constitutive thiolase promoter. The C. beijerinckii _SDR and C. beijerinckii NCIMB 8052 wildtype were used for comparative fermentation of non-detoxified and detoxified hydrothermolysis-pretreated switchgrass hydrolysates (SHs) with and without (NH 4 ) 2 CO 3 supplementation. In the absence of (NH 4 ) 2 CO 3 , fermentation of non-detoxified SH with C. beijerinckii _SDR resulted in the production of 3.13- and 2.25-fold greater quantities of butanol (11.21 g/L) and total ABE (20.24 g/L), respectively, than the 3.58 g/L butanol and 8.98 g/L ABE produced by C. beijerinckii _wildtype. When the non-detoxified SH was supplemented with (NH 4 ) 2 CO 3 , concentrations were similar for butanol (9.5 compared with 9.2 g/L) and ABE (14.2 compared with 13.5 g/L) produced by C. beijerinckii _SDR and C. beijerinckii _wildtype, respectively. Furthermore, when C. beijerinckii _SDR and C. beijerinckii _wildtype were cultured in detoxified SH medium, C. beijerinckii _SDR produced 1.11- and 1.18-fold greater quantities of butanol and ABE, respectively, than when there was culturing with C. beijerinckii _wildtype. When the combined results of the present study are considered, conclusions are that the microbial strain and medium modifications of the fermentation milieu resulted in greater production of fuels and chemicals from non-detoxified LB hydrolysates.more » « less