Exogenous inoculation of Klebsiella and Saccharomyces enhances core community stability and tea quality in short-term piling fermentation of Tianjian dark tea

Short-term piling fermentation (≤ 24 hours) is critical process to produce Tianjian dark tea, but its stability and quality control face a very significant challenge. In this study, the effect of exogenously mixed inoculation with bacterial Klebsiella and fungal Saccharomyces on microbial community and tea quality was first investigated during short-term piling fermentation. The results show that exogenous inoculation significantly enhanced the conversion efficiency of key components. Compared to the control, the tea polyphenols and catechins in the inoculation decreased by 33.56% and 53.98%, respectively, while the theabrownin and flavonoids increased by 112.17% and 9.1%, respectively, improving the tea quality of short-term piling. Community and network analyses indicated that the inoculation reshaped the microbial community, accelerated piling initiation, and strengthened microbial interactions and cooperative metabolism. Random Forest and Mantel test further revealed that the enhancement in piling quality was achieved by strengthening the stability and interaction network of core microbial community. This study not only helps understand the biochemical evolution during inoculated short-term piling fermentation but also provides a theoretical basis for regulating microbial community in short-term piling fermentation to ensure the consistent piling quality of Tianjian dark tea. • Exogenously mixed inoculation in Tianjian dark tea piling was first studied • Inoculation accelerated initiation of short-term piling fermentation (24 h) • Inoculation enhanced core microbial community and interaction network • Inoculation promoted key compounds conversion to improve piling quality