Engineering Thermoanaerobacterium aotearoense SCUT27 with the deficiency of a hypothetic protein regulated by ArgR1864 for enhanced ethanol production from lignocellulosic hydrolysates

Abstract

Arginine repressor (ArgR1864) is a multifunctional regulator in Thermoanaerobacterium aotearoense SCUT27 (SCUT27). For better understanding its function in SCUT27, the transcriptome of SCUT27/ΔargR1864 under xylose was further investigated. 2014 (V518_2014) denoted as a hypothetic protein gene was mined, which played important roles on xylose metabolism and carbon metabolic flux distribution in SCUT27. In 2014 deletion mutant, no lactic acid could be produced along with enhanced ethanol formation. Same changes were also observed in SCUT27/ΔargR1864. ArgR1864 is the direct regulator of 2014 identified by electrophoretic mobility shift assays (EMSA). When 2014 was complemented in SCUT27/ΔargR1864, the fermentation traits of SCUT27/ΔargR1864/2014 were returned to wild-type levels, suggesting that the improved xylose utilization and ethanol formation of SCUT27/ΔargR1864 were attributed to the low expression of 2014. When cultured under sorghum stalk, corn cob and wheat straw hydrolysates, SCUT27/Δ2014 also showed the excellent capability for sugar utilization and ethanol production with the consumption rate of xylose and glucose increased by 20%–37.93 and 64.29%–190.91% separately, the ethanol production improved by 326.61%–547.89% and ethanol yield enhanced by 216.67%–337.50%. Thus, 2014, as a hypothetic protein gene, could be used as the new genetic reference to predict functional genes to engineer the microorganism for biofuel production from lignocellulosic hydrolysates.