Research on lactic acid bacterial metabolism has already stepped into a new era. This review summarizes the current research on sugar, citric acid and protein metabolism in lactic acid bacteria, as well as the application of genomics, comparative genomics and metagenomics based on next-generation sequencing technology in studies of lactic acid bacterial metabolism. It is expected that this review will provide theoretical support for further research of lactic acid bacterial metabolism.

The optimization of medium components and culture conditions for improved spore production of Monascus purpureus M-4 in submerge culture was performed using a combination of one-factor-at-a-time (OFAT) method and response surface methodology (RSM). The OFAT results showed that potato extract powder and glucose were the optimal nitrogen and carbon source, respectively and that their optimal concentrations were 0.4 and 2.0 g/100 mL, respectively. The optimal culture conditions that provided the maximum number of spores were as follows: initial medium pH 6.72 (natural pH), medium volume in a 500-mL triangular flask 120 mL, concentration of added CaCO3 2.0 g/100 mL, number of passages 2, and culture time 72 h. Potato extract powder and glucose concentration as well as culture time were identified as main variables that influence spore production and their optimal levels were determined to be respectively 0.38 g/100 mL, 2.2 g/100 mL and 6.5 d using RSM. The highest spore number of (7.47 ± 0.15) × 106 CFU/mL was experimentally obtained under the optimized conditions, which was close to the predicted value (7.53 ± 0.31) × 106 CFU/mL. The average error between the predicted and experimental values was 0.79%. A 31.13-fold increase in spore number was achieved by the optimization. Besides, the spore-producing ability per unit volume of strain M-4 was greatly improved.