Due to energy and environmental concerns, biobutanol is gaining increasing attention as an alternative renewable fuel owing to its desirable fuel properties.

Resveratrol, an ingredient of traditional Chinese medicine, has beneficial effects on human health and huge potential for application in modern medicine. Polydatin is extracted from plants and then deglycosylated into resveratrol; enzymatic methods are preferred for this reaction. In this study, a β-D-glucosidase from Sphingomonas showed high efficiency in transforming polydatin into resveratrol and was tolerant toward organic solvents. Applying this enzyme in a biphasic transformation system resulted in 95.3% conversion of 20% concentration crude polydatin to resveratrol in 4 h. We thus report a new method for high-efficiency, clean production of resveratrol.

Background: The four-carbon alcohol, butanol, is emerging as a promising biofuel and efforts have been undertaken to improve several microbial hosts for its production. However, most organisms have very low tolerance to n-butanol (up to 2% (v/v)), limiting the economic viability of butanol production. Although genomic tools (transcriptomics, proteomics, and metabolomics) have been widely used to investigate the cellular response to butanol stress, the existing knowledge of the molecular mechanisms involved in butanol tolerance is limited, and strain improvement is difficult due to the complexity of the regulatory network. Results: In this study, a butanol-tolerant Escherichia coli was constructed by disrupting gene astE (encoding succinylglutamate desuccinylase) to obtain higher butanol tolerance (increased by 34.6%). To clarify the tolerance mechanism, a metabolome analysis was also performed. As a result, a total of 73 metabolites (11 elevated and 62 decreased) were significantly changed. Most of the downregulated metabolites were mainly involved in the L-arginine degradation pathway, sulfate metabolic pathway, and 2-methylcitrate metabolic pathway. To further analyze the differential gene expression, a transcriptome was created. In total, 311 genes (113 upregulated and 198 downregulated) showed over a twofold difference and were associated with carbohydrate metabolism, energy metabolism, and ABC transporters. The integration of metabolomics and transcriptomics found that acid-activated glutaminase ybaS and the amino acid antiporter gadC were significantly up-regulated, but the levels of L-arginine and glutamate were not significantly increased and decreased. Therefore, the changes of amino acids between strains BW25113 and BW25113-ΔastE were measured by amino acid analysis. The ability of a mutant strain against acid stress was also measured by the growth experiment under various pH conditions in the absence of butanol. Conclusions: Based on the above experiments, it could be concluded that mutant BW25113-ΔastE mainly regulated intracellular pH-homeostasis to adapt to butanol stress, indicating the non-negligible impact of pH on microbial butanol tolerance, broadening our understanding of microbial butanol tolerance and providing a novel strategy for the rational engineering of a more robust butanol-producing host.

A heterologous pathway for sucrose transport and metabolism was introduced into Clostridium beijerinckii to improve sucrose use for n -butanol production. The combined expression of StSUT1 , encoding a sucrose transporter from potato ( Solanum tuberosum ), and SUC2 , encoding a sucrose invertase from Saccharomyces cerevisiae , remarkably enhanced n -butanol production. With sucrose, sugarcane molasses and sugarcane juice as substrates, the C. beijerinckii strain harbouring StSUT1 and SUC2 increased acetone–butanol–ethanol production by 38.7%, 22.3% and 52.8%, respectively, compared with the wild-type strain. This is the first report to demonstrate enhanced sucrose fermentation due to the heterologous expression of a sucrose transporter and invertase in Clostridium . The metabolic engineering strategy used in this study can be widely applied in other microorganisms to enhance the production of high-value compounds from sucrose-based biomass.

A convenient and effective sucrose transport assay for Clostridium strains is needed. Traditional methods, such as ¹⁴C-sucrose isotope labelling, use radioactive materials and are not convenient for many laboratories. Here, a sucrose transporter from potato was introduced into Clostridium, and a fluorescence assay based on esculin was used for the analysis of sucrose transport in Clostridium strains. This showed that the heterologously expressed potato sucrose transporter is functional in Clostridium. Recombinant engineering of high-level sucrose transport would aid sucrose fermentation in Clostridium strains. The assay described herein provides an important technological platform for studying sucrose transporter function following heterologous expression in Clostridium.