Dahong Wang

Environmental pH plays a critical role in microbial fermentation processes. Weizmannia coagulans attracts particular attention for exceptional acid tolerance and lactic acid productivity. Yet acidic stress impacts on its cell division regulation remain unclear. Here, a critical pH value (pH 4.20) for growth inhibition of the Gram-positive bacterium Weizmannia coagulans strain BC99 was first established. Transcriptomic analysis of metabolic pathways was then performed. The multi-layered regulatory network underlying acid stress-induced cell division was elucidated. Integrated transcriptomic and physiological analyses reveal that acid stress triggers multigene expression reprogramming. This drives core metabolic network reorganization, coordinately regulating division processes. RNA-seq analysis demonstrated acid stress triggered differential expression of division genes (FtsZ/Q downregulation), ATP synthase suppression, and peptidoglycan transport reduction, while enhancing membrane rigidification (Cfa) and magnesium homeostasis (CorA). The PhoPR dual-component system emerged as a central regulator, inhibiting septal assembly via RipA hydrolase and RpsU ribosomal suppression while rerouting carbon flux to glycolysis, elucidating bacterial acid adaptation mechanisms. Collectively, these adaptive changes prioritize cell survival over active proliferation under acidic conditions. This study provides molecular insights into how W. coagulans preserves viability under acid stress, offering a theoretical basis for optimizing its performance in probiotic applications.

Forsythia suspensa black tea (FSBT) is highly favored by consumers due to its excellent flavor and potential health benefits. However, its key aroma components are unclear. In this study, HS-SPME-GC×GC-TOF/MS combined with GC-O, rOAV, aroma recombination and omission experiments were used to analyze key aroma compounds in FSBT. Sensory evaluation showed that FSBT had a pure aroma, medicinal fragrance, floral and sweet notes. A total of 153 volatiles were identified, predominantly consisting of hydrocarbons, alcohols, and aldehydes. Based on rOAV and GC-O, 63 odor-active compounds were identified. In addition, aroma recombination model effectively simulates the overall aroma characteristics of FSBT. Omission experiments showed that 32 key odor-active compounds play a crucial role in shaping the aroma of FSBT. Among them, benzyl alcohol, linalool, benenethanol, benenacetalhydrate, β-damascenone are of great significance for the aroma of FSBT. This study provides a fundamental theoretical framework for the processing and quality control of FSBT.

To explore an industrial fermentation approach for traditional mung bean sour pulp, this study isolated core microorganisms including lactic acid bacteria and yeasts from naturally fermented samples and constructed a synthetic microbial community. The optimized community consisted of Lactiplantibacillus pentosus, Lactococcus garvieae, and Cyberlindnera jadinii at a ratio of 7:3:0.1 and was used to ferment cooked mung bean pulp with a material-to-water ratio of 1:8 and 1% sucrose addition. Under these conditions, the final product exhibited significantly higher levels of protein (4.55 mg/mL), flavonoids (0.10 mg/mL), polyphenols (0.11 mg/mL), and vitamin C (7.75 μg/mL) than traditionally fermented mung bean sour pulp, along with enhanced antioxidant activity. The analysis of organic acids, free amino acids, and volatile compounds showed that lactic acid was the main acid component, the bitter amino acid content was reduced, the volatile flavor compounds were more abundant, and the level of harmful compound dimethyl sulfide was significantly decreased. These results indicate that fermentation using a synthetic microbial community effectively improved the nutritional quality, flavor, and safety of mung bean sour pulp.