Noni (Morinda citrifolia L.) has been recognized as an important herb for treating various physiological disorders worldwide. Fermented noni fruit juice, established as a novel food in European Union, is the most important noni product. However, the structure, functions and enzyme profiles of microbiome during fermentation remain unclear. The metatranscriptomic was used to comprehensively explore the active microbial community and key metabolic function. Acetobacter sp., Acetobacter aceti and Gluconobacter sp. were the major microorganisms and appeared in succession during fermentation. According to principal components analysis (PCA) of metabolism-related unigenes by KEGG database, the fermentation process was divided into three stages and almost completed at the end of the second stage. Furthermore, carbohydrate-active enzymes (CAZymes) and the expression of key enzymes in major metabolic pathways were analyzed systematically. Analysis by HS-SPME-GC–MS and odor active value (OAV) revealed that butanoic acid and hexanoic acid were the main volatile compounds for the unpleasant odor of fermented noni fruit juice. The microbiome in the fermentation process lacked key enzymes that degrade butanoic acid and hexanoic acid, which imparted rancid and sweat odor. This study provides theoretical basis for product improvement and new product development, thus promoting the development of noni food industry.

诺丽（Morinda citrifolia L.）已被公认为是治疗全世界各种生理疾病的重要草药。发酵诺丽果汁在欧盟被确立为一种新型食品，是最重要的诺丽产品。但是，发酵过程中微生物组的结构，功能和酶谱仍然不清楚。转录组学被用来全面探索活跃的微生物群落和关键的代谢功能。醋杆菌属。，醋杆菌和葡糖杆菌sp。是主要微生物，在发酵过程中连续出现。根据KEGG数据库对代谢相关单基因的主成分分析（PCA），发酵过程分为三个阶段，并在第二阶段结束时基本完成。此外，系统分析了碳水化合物活性酶（CAZymes）和主要代谢途径中关键酶的表达。通过HS-SPME-GC-MS和气味活性值（OAV）进行的分析表明，丁酸和己酸是导致发酵诺丽果汁难闻气味的主要挥发性化合物。发酵过程中的微生物组缺乏降解丁酸和己酸的关键酶，这些酶会产生腐臭和汗味。该研究为产品改进和新产品开发提供了理论基础，