One strategy to increase the yield of desired fermentation products is to redirect substrate carbon from biomass synthesis. Nongenetic approaches to alter metabolism may have advantages of general applicability and simple control. The goal of this study was to identify and evaluate chemicals for their ability to inhibit the growth of Saccharomyces cerevisiae while allowing ethanol production with higher yields. Eight potential growth-inhibitory chemicals were screened for their ability to reduce cell growth in 24-well plates. Effective chemicals were then evaluated in cultivations to identify those that simultaneously reduced biomass yield and increased ethanol yield. The yeast quorum-sensing molecules 2-phenylethanol, tryptophol and tyrosol were found to increase the ethanol yield of S. cerevisiae JAY 270. These molecules were tested with seven other yeast strains and ethanol yields of up to 15% higher were observed. The effects of 2-phenylethanol and tryptophol were also studied in bioreactor fermentations. These findings demonstrate for the first time that the ethanol yield can be improved by adding yeast quorum-sensing molecules to reduce the cell growth of S. cerevisiae, suggesting a strategy to improve the yield of ethanol and other yeast fermentation products by manipulating native biological control systems.

Coal-derived soil amendments have been shown to improve soil physicochemical properties and promote plant growth; however, their effects on rhizosphere microbial communities remain insufficiently understood. In this study, a comprehensive assessment of the impacts of a lignite coal-based, microbially processed amendment on lettuce (Lactuca sativa) growth, soil properties, and rhizosphere microbiota was conducted. Application of the coal-based amendment resulted in a more than two-fold increase in plant fresh weight compared to untreated soil. The amendment significantly improved soil organic matter content but did not increase phosphate or potassium levels. Rhizosphere bacterial and fungal communities were profiled using 16S rRNA and ITS gene sequencing. Principal coordinate analysis revealed that the coal-based amendment, commercial organic fertilizer, and raw coal each induced distinct shifts in microbial community structure. Notably, treatment with the coal-based amendment reduced the relative abundance of Proteobacteria while increasing Acidobacteriota and Chloroflexi in the bacterial community. In fungal communities, the amendment decreased Basidiomycota and enriched Ascomycota. These results suggest that the observed enhancement in plant growth is closely linked to changes in rhizosphere microbial composition and soil organic matter content, highlighting the potential of microbially processed coal products as sustainable soil amendments in agriculture.