Metabolomics-Driven Elucidation of Interactions between Saccharomyces cerevisiae and Lactobacillus panis from Chinese Baijiu Fermentation Microbiome

Saccharomyces cerevisiae and Lactobacillus panis are ethanol and lactic acid producers in Maotai-flavor Baijiu fermentation. Understanding their interaction is important to regulate the microbiome composition during fermentation and biosynthesis of ethanol and lactic acid. This study is the first to analyze the interaction between S. cerevisiae and L. panis at different growth phases during co-cultivation. Results showed that the different growth phases of S. cerevisiae modulated L. panis growth. Metabolomics analysis showed that amino acids and nucleoside secreted by S. cerevisiae promote L. panis growth, while ethanol inhibited L. panis growth. Furthermore, S. cerevisiae modulated L. panis cell growth under varying sugar concentrations. Simulated solid-state fermentation demonstrated that regulating the sugar concentration or the ratio of S. cerevisiae to L. panis could inhibit L. panis cell growth and reduce lactic acid accumulation. This study provided an understanding on Maotai-flavor Baijiu microbiome, which might be useful for metabolite regulation.

The effect of anaerobic co-fermentation on acidification performance of food waste and cardboard waste

The fermentation system with high solid materials for food waste (FW) is uneven in nutrition and easy to produce volatile acid accumulation, which causes the reaction system to acidify and affects the normal operation of fermentation. This study evaluated the effect of the co-substrate percentages (FW:CB = 9:1, FW:CB = 8:2, FW:CB = 7:3) and the initial total solid contents (12%, 15%, 18%) on the co-fermentation acidification performance of FW and cardboard waste (CB). The maximum methane production was obtained when mono-fermenting FW had high solids contents(1.4 L/kg). The methane production increased and then decreased with the increasing percentages of CB. Under the conditions of FW:CB = 8:2, the maximum methane production could reach 3.4 L/kg. The lower methane production (1.8 ∼ 2.5 L/kg) with high percentages of CB (FW:CB = 7:3) was translated into higher yields of caproic acid (up to 26%), which indicated lower percentages of CB had a stabilization effect due to the higher buffering capacities in co-fermentation. As a result, this study demonstrated new possibilities for using CB percentages to control the production of high added-value biogas in dry co-fermentation of FW.

Methylation Profiling of Biosynthetic Genes Reveals The Role of D-Galacturonic Acid Reductase In Ascorbic Acid Accumulation In Tomato Fruit

Ascorbic acid (AsA) is an important nutrient component contributing to major flavor value of tomato fruit and human health. Although transcription regulation of AsA biosynthetic genes have been well demonstrated, epigenetic modification underlying AsA accumulation remains unclear. In this study, we exposed immature tomato fruits to a methyltransferase inhibitor (5-azacytidine) and detected the impacts on AsA accumulation. Inhibition of DNA methylation enhanced AsA accumulation in tomato leaves and fruits. We further isolated a AsA biosynthetic gene, SlGalUR5, which encodes a D-galacturonic acid reductase. SlGalUR5 showed reduced DNA methylation levels and higher transcription levels in Slmet1 mutant while have converse pattern in Sldml2 mutant. 5-azacytidine treatment significantly decreased DNA methylation levels of SlGalUR5 in fruits. Conversely, transcription profiles of SlGalUR5 and enzyme activity of GalUR were enhanced in 5-azacytidine–treated fruits. Our finding revealed a new insight into epigenome modification of SlGalUR5 involved in ascorbic acid accumulation and provide a potential means of increasing AsA levels for tomato breeding.

GOLDEN TANGERINE TOMATO ROOTS SHOW INCREASED ACCUMULATION OF ACYCLIC CAROTENOIDS, LESS ABSCISIC ACID, DROUGHT SENSITIVITY, AND IMPAIRED ENDOMYCORRHIZAL COLONIZATION

Heirloom golden tomato fruit varieties are highly nutritious as they accumulate tetra-cis-lycopene, which has a higher bioavailability and recognised health benefits in treating anti-inflammatory diseases compared to all-trans-lycopene isomers found in red tomatoes. We investigated if photoisomerization of tetra-cis-lycopene occurs in roots of the golden tangerine Micro-Tom variety (tangmic), and how this affects root to shoot biomass, mycorrhizal colonization, abscisic acid accumulation, and responses to drought. tangmic plants grown in soil under glasshouse conditions displayed a reduction in height, number of flowers, fruit yield, and root length compared to wild type (WT). Soil inoculation with Rhizophagus irregularis revealed fewer arbuscules and other fungal structures in the endodermal cells of roots in tangmic relative to WT. The roots of tangmic hyperaccumulated acyclic cis-carotenes, while only trace levels of xanthophylls and abscisic acid were detected. In response to a water deficit, leaves from the tangmic plants displayed a rapid decline in maximum quantum yield of photosystem II compared to WT, indicating a defective root to shoot signalling response to drought. The lack of xanthophylls biosynthesis in tangmic roots reduced abscisic acid levels, thereby likely impairing endomycorrhiza colonisation and drought-induced root to shoot signalling.