Engineered yeast tolerance enables efficient production from toxified lignocellulosic feedstocks

Abstract

Lignocellulosic biomass remains unharnessed for the production of renewable fuels and chemicals due to challenges in deconstruction and the toxicity its hydrolysates pose to fermentation microorganisms. Here, we show in Saccharomyces cerevisiae that engineered aldehyde reduction and elevated extracellular potassium and pH are sufficient to enable near-parity production between inhibitor-laden and inhibitor-free feedstocks. By specifically targeting the universal hydrolysate inhibitors, a single strain is enhanced to tolerate a broad diversity of highly toxified genuine feedstocks and consistently achieve industrial-scale titers (cellulosic ethanol of >100 grams per liter when toxified). Furthermore, a functionally orthogonal, lightweight design enables seamless transferability to existing metabolically engineered chassis strains: We endow full, multifeedstock tolerance on a xylose-consuming strain and one producing the biodegradable plastics precursor lactic acid. The demonstration of “drop-in” hydrolysate competence enables the potential of cost-effective, at-scale biomass utilization for cellulosic fuel and nonfuel products alike.

l-Lactic Acid Production Using Engineered Saccharomyces cerevisiae with Improved Organic Acid Tolerance

“…The cell growth, lactic acid production, and ethanol production of BK01 were significantly better than SR8LDH under the acetic acid stress. Lactic acid production by engineered S. cerevisiae was demonstrated mostly using complex and synthetic medium [50], and cellulosic lactic acid production was reported only in a few recent studies [8,51]. Using spent coffee ground hydrolysates and wheat straw hydrolysates, 11.5 g/L [8] and 10 g/L [51] lactic acid were produced.…”

“…Lactic acid production by engineered S. cerevisiae was demonstrated mostly using complex and synthetic medium [50], and cellulosic lactic acid production was reported only in a few recent studies [8,51]. Using spent coffee ground hydrolysates and wheat straw hydrolysates, 11.5 g/L [8] and 10 g/L [51] lactic acid were produced. The increases in media potassium (K + ) and pH were able to improve cellulosic lactic acid production significantly [51].…”

“…Using spent coffee ground hydrolysates and wheat straw hydrolysates, 11.5 g/L [8] and 10 g/L [51] lactic acid were produced. The increases in media potassium (K + ) and pH were able to improve cellulosic lactic acid production significantly [51]. Additionally, the overexpression of GRE2 with detoxifying activity toward fermentation inhibitors in cellulosic biomass hydrolysates (furfural and hydroxymethylfurfural) contributed to further improvement in cellulosic lactic acid production.…”

Microbial Utilization of Next-Generation Feedstocks for the Biomanufacturing of Value-Added Chemicals and Food Ingredients

“…However, ethanol is mainly produced from starch-based resource, e.g., corn, which competes with food applications and loses 1/3 of carbon as CO 2 ( Table 1 ). Although ethanol production from lignocellulose still faces technical challenges and the U.S. Cellulosic Ethanol Industry has dwindled sharply ( Lam et al, 2021 ), technological advance can reinvigorate the industry especially by reducing the overall cost especially from lignocellulose pretreatment. Acetate is currently produced from carbonylation of methanol (the main route) and sugar fermentation (used in food applications) ( Table 1 ).…”

Industrialization progress of lignocellulosic ethanol

“…The developed countries such as United States, Brazil, and Europe heavily invested in research and development (R&D) [3]. The process of ethanol production from lignocellulosic biomass is theoretically feasible; however, a few bottlenecks have affected the development of the industry, from the collection, transportation, and storage system of raw materials to the pretreatment technology of raw materials for destroying the anti-degradation barrier [4,5], from the analysis and reconstruction of microorganisms with complex cellulose-degrading enzyme system to the screening and construction of fermentation strain for efficient conversion of cellulose sugar [6,7], There are many scientific, technical, and engineering problems which need to be explored and solved properly. Further improving and perfecting the production technology of lignocellulosic ethanol and improving its economic competitiveness have become the key to the success or failure of lignocellulosic ethanol industrialization [8].…”