Enhanced production of pleuromutilin by Pleurotus mutilus and study on its molecular structure.

This study aims to enhance the accumulation of pleuromutilin by Pleurotus mutilus and to analyze the molecular structure of pleuromutilin. The results showed that a novel three-stage DO control strategy (60% DO, 1-3d; 45% DO, 4-6d; 30% DO, 7-9d) was very effective for improving the pleuromutilin accumulation and the highest production reached 12g/L, a 4-fold increase over a constant DO strategy. Furthermore, the flow behavior of fermentation broth appeared Newtonian with a maximum µap of 3.9×10-3Pa·s. Meanwhile the molecular formula (C22H34O5), molecular weight (378.5) and structural formula of pleuromutilin were concluded based on spectroscopy and element assay. The main components were hydroxyl, methyl, methylene, carbonyl, carboxyl, and polycyclic hydrocarbon. This work demonstrated that DO strategy was suitable for scalable production of pleuromutilin, which makes pleuromutilin more affordable as materials in food.

The response of Serratia marcescens JG to environmental changes by quorum sensing system.

Many bacterial cells are known to regulate their cooperative behaviors and physiological processes through a molecular mechanism called quorum sensing. Quorum sensing in Serratia marcescens JG is mediated by the synthesis of autoinducer 2 (AI-2) which is a furanosyl borate diester. In this study, the response of quorum sensing in S. marcescens JG to environment changes such as the initial pH, carbon sources and boracic acid was investigated by a bioreporter and real-time PCR analysis. The results show that glucose can affect AI-2 synthesis to the greatest extent, and 2.0 % glucose can stimulate S. marcescens JG to produce more AI-2, with a 3.5-fold increase in activity compared with control culture. Furthermore, the response of quorum sensing to changes in glucose concentration was performed by changing the amount of luxS RNA transcripts. A maximum of luxS transcription appeared during the exponential growth phase when the glucose concentration was 20.0 g/L. AI-2 production was also slightly impacted by the low initial pH. It is significant for us that the addition of boracic acid at microdosage (0.1-0.2 g/L) can also induce AI-2 synthesis, which probably demonstrated the feasible fact that the 4,5-dihydroxy-2, 3-pentanedione cyclizes by the addition of borate and the loss of water, is hydrated and is converted to the final AI-2 in S. marcescens JG.