Significance and Impact of the Study: The ex situ application of rhamnolipid for microbial enhanced oil recovery (MEOR) is costly and complex in terms of rhamnolipid production, purification and transportation. Compared with ex situ applications, the in situ production of rhamnolipid in anaerobic oil reservoir is more advantageous for MEOR. This study is the first to report the anaerobic production optimization of rhamnolipid. Results showed that the optimized medium enhanced not only the anaerobic production of rhamnolipid but also crude oil recovery. Core flooding test results also revealed that Ps. stutzeri Rhl grown in an optimized medium enhanced the oil recovery efficiency by 15Á7%, which was 6Á6% higher than in the initial medium. Results suggested that the optimized medium is a promising nutrient source that could effectively mobilize oil by enhancing the in situ production of rhamnolipid.

Significance and Impact of the Study: KB2194-320, a combination of two bacterial strains bred by spaceflight mutation, exhibited significantly improved 2-KLG productivity and hence could potentially increase the efficiency and reduce the cost of vitamin C production by the two-step fermentation process. In addition, a new pH indicator method was applied for rational screening of K2, which dramatically improved the efficiency of screening. AbstractTwo bacterial strains used for industrial production of 2-keto-L-gulonic acid (2-KLG), Ketogulonigenium vulgare 2 and Bacillus thuringiensis 1514, were loaded onto the spacecraft Shenzhou VII and exposed to space conditions for 68 h in an attempt to increase their fermentation productivities of 2-KLG. An optimal combination of mutants B. thuringiensis 320 and K. vulgare 2194 (KB2194-320) was identified by systematically screening the pH and 2-KLG production of 16 000 colonies. Compared with the coculture of parent strains, the conversion rate of L-sorbose to 2-KLG by KB2194-320 in shake flask fermentation was increased significantly from 82Á7% to 95Á0%. Furthermore, a conversion rate of 94Á5% and 2-KLG productivity of 1Á88 g l À1 h À1 were achieved with KB2194-320 in industrial-scale fermentation (260 m 3 fermentor). An observed increase in cell number of K2194 (increased by 47Á8%) during the exponential phase and decrease in 2-KLG reductase activity (decreased by 46Á0%) were assumed to explain the enhanced 2-KLG production. The results suggested that the mutants KB2194-320 could be ideal substitutes for the currently employed strains in the 2-KLG fermentation process and demonstrated the feasibility of using spaceflight to breed high-yielding 2-KLGproducing strains for vitamin C production.