Consolidated bioprocessing (CBP) has been widely adopted as a cost-effective strategy for the bioconversion of lignocellulosic biomass into bio-chemicals. Microbial consortium can complete the complex CBP processes through the cooperation of different microorganisms. In this study, a synthetic microbial consortium was designed, which is composed of a hemicellulase-producing bacterium Thermoanaerobacterium thermosaccharolyticum and succinic acid production specialist Actinobacillus succinogenes 130Z. The simultaneous conversion of xylose hydrolyzed by T. thermosaccharolyticum could maintain a high hydrolyzing rate, which would facilitate succinic acid production by A. succinogenes 130Z. After process optimization, 32.50 g/L of succinic acid with yield of 0.41 g/g was obtained from 80 g/L xylan through CBP, representing the highest succinic acid production directly from hemicellulose materials. In addition, 12.51 g/L of succinic acid was directly produced from 80 g/L of corn cob. The above results demonstrated that this CBP based microbial co-cultivation system had great potential to convert lignocellulosic biomass into various bio-chemicals.
A unique Meyerozyma sp. strain YLG18 was obtained in this study, which was capable of producing 2-phenylethanol through both Ehrlich and Shikimate pathways. Response surface methodology (RSM) was implemented to improve the maximum 2-PE production. At optimized conditions: temperature, 24.7℃; initial glucose, 63.54 g/L; initial L-phe, 10.70 g/L, 2-PE production was increased to 2.55 g/L, leading to 104% increase compared to the pre-optimized one. In situ product recovery (ISPR) could further help improve the final 2-PE production to 3.20 g/L with fatty acid methyl ester as the extractant, representing the highest 2-PE production by using Meyerozyma sp.. Furthermore, genes involved in 2-PE synthesis were identified and their expression levels between Shikimate pathway and Ehrlich pathway were compared. Based on the genomic and transcriptional analysis, a penta-functional enzyme AroM in Shikimate pathway and an aspartate aminotransferase (AAT) with the potential to convert phenylalanine into phenylpyruvate in Ehrlich pathway were identified. These findings would help broaden our knowledge and add to the pool of known 2-PE generating microbes and genes.