BACKGROUND: Optically pure acetoin is an important potential pharmaceutical intermediate. It has also been widely used to synthesize novel optically active α-hydroxyketone derivatives and liquid crystal composites. Recombinant Escherichia coli was developed for efficient (3R)-acetoin production. Culture medium optimization and process control were carried out to improve (3R)-acetoin yield by the engineered strain. RESULTS: A synthetic pathway involved the budRAB genes from Serratia marcescens and NADH oxidase gene fromLactobacillus brevis in E. coli was developed for efficient (3R)-acetoin production. Batch culture showed that 23.4 g L −1 of (3R)-acetoin could be obtained from 60 g L −1 glucose by the engineered strain. Chiral-column GC analysis indicated that the stereoisomeric purity of (3R)-acetoin produced was 97.3%. Further, the medium composition was optimized in shake flasks by an orthogonal design method. Under optimal conditions, (3R)-acetoin concentration reached 38.3 g L −1 in flask fermentation. Fed-batch fermentation based on a suitable agitation speed was carried out in a 5 L bioreactor, and maximum (3R)-acetoin concentration of 60.3 g L −1 was achieved with a productivity of 1.55 g L −1 h −1 and yield 86.3%. CONCLUSION: An engineering E. coli for efficient (3R)-acetoin production was constructed. The optimization of fermentation variables and fed-batch culture resulted in a maximum (3R)-acetoin concentration of 60.3 g L −1 . DISCUSSIONChiral AC has recently been paid increasing attention due to its potential industrial and pharmaceutical applications. 7 However, natural microorganisms usually produce a mixture of (3R)-AC and (3S)-AC, which is difficult to accumulate due to a large J Chem Technol Biotechnol 2015; 90: 93-100

Artificial municipal wastewater was treated successfully by the bioaugmentation of Bacillus sp. K5 capable of simultaneous nitrification and denitrification (SND) within a sequencing batch reactor (SBR). During the long-term operation, the bioaugmentation system exhibited an excellent and steady COD and NH4+-N removal without nitrite and nitrate accumulation. The average removal efficiency for COD and NH4+-N achieved to 98% and 95%, respectively. PCR-DGGE, SEM and FISH revealed that the introduced Bacillus sp. K5 should be an important functional strain and exerted a critical influence on the structure of microbial community. qPCR analysis indicated that the strain K5 facilitated aerobic nutrients removal capabilities and SND might be the primary pathway for the nitrogen removal in the SBR. Overall, the SBR system used in our study should be very promising for the future wastewater treatment.

This work evaluates the efficiency of ammonium removal from piggery wastewater using a sequencing batch reactor (SBR) inoculated with a newly isolated strain of Pseudomonas putida HJH1. The strain HJH1 not only could survive and remove up to 72.4 mg/L NO 2 --N under aerobic conditions, but it also has good performance for simultaneous nitrification and denitrification (SND) with no nitrite accumulation. The SBR system was able to consistently remove: 1) 76.4-100% ammonium nitrogen and 71.4-100% COD from artificial wastewater in stage 1, and 2) 89.2-99.1% ammonium nitrogen and 82.4-100% COD from piggery wastewater in stage 2. During the whole operation, the strain HJH1 predominated in the SBR all the time to function together with other bacteria. Results indicated that the SBR system inoculated with Pseudomonas putida HJH1 can efficiently remove ammonium nitrogen from piggery wastewater, thereby having potential applications for future nitrogen removal.