Using ectoine-excreting strain Halomonas salina DSM 5928(T), we developed a new process for high-efficiency production of ectoine, which involved a combined process of batch fermentation by growing cells and production by resting cells. In the first stage, batch fermentation was carried out using growing cells under optimal fermentation conditions. The second stage was the production phase, in which ectoine was synthesized and excreted by phosphate-limited resting cells. Optimal conditions for synthesis and excretion of ectoine during batch fermentation in a 10 l fermentor were 0.5 mol l(-1) NaCl and an initial monosodium glutamate concentration of 80 g l(-1) respectively. The pH was adjusted to 7.0 and the temperature was maintained at 33°C. In phosphate-limited resting cells medium, monosodium glutamate and NaCl concentration was 200 g l(-1) and 0.5 mol l(-1), respectively, as well as pH was 7.0. The total concentration of ectoine produced was 14.86 g l(-1), the productivity and yield of ectoine was 7.75 g l(-1) day(-1) and 0.14 g g(-1), respectively, and the percentage of ectoine excreted was 79%. These levels of ectoine production and excretion are the highest reported to date.

Four individual lactic acid bacteria strains (LABs), including Lactobacillus plantarum, Lactobacillus reuteri, Lactobacillus rhamnosus, and Pediococcus pentosaceus, were used for the fermentation of Kuqa apple juice (KAJ). This work investigated the effects of four individual LABs on physical and chemical and antioxidant properties of fermented KAJ. In addition, this study combined sensory evaluation to select one or two suitable strains for fermenting KAJ. The results showed that P. pentosaceus had the fastest speed for fermentation. The maximum SOD activity of L. plantarum reached 284.33 U/ml. The TPC of L. reuteri had a high value of 94.00 mg/L. The DPPH-free radical scavenging activity of L. plantarum eventually reached 97.90%, while the sensory evaluation of P. pentosaceus was the best with a 94% of GM value, followed by L. plantarum. Moreover, the major organic acid in fermented KAJ was malic acid. In summary, different strains have different effects on the characteristics of fermented KAJ, but in general, P. pentosaceus and L. plantarum are the most capable for fermenting KAJ. Novelty impact statement:The work provided the first research about malolactic fermentation for apples in Kuqa County, Xinjiang Province, China, which provided a new type of preservation technology for Kuqa apples and solved the problem of local apple with short storage period but high production. In addition, this work obtained the two most suitable strains for fermentation of Kuqa apple juice. In summary, this result provided a theoretical basis for the fermentation of Kuqa apple juice and enhanced economic benefits for the Kuqa apple industry. Highlights• This work research more than three kinds of individual lactic acid bacteria compared with other work.• There is no study about kuqa apple juice.The apples used come from Kuqa County, Xinjiang, China. As Kuqa County has sufficient sunlight and large temperature difference between day and night, the apples in Kuqa County are rich in nutrients and high in maturity.• This work belongs to bioengineering, so it plays an important role for the practical mean for apple industry. | MATERIAL S AND ME THODS | Materials, microbial strains, and enzymesTen kilograms of fresh apples were purchased from the fruit shop of Xinjiang University. Ethanol, gallic acid, and Folin-Ciocalteu phenol were got from Tianjin Shengao Chemical Reagent (Tianjin, China). The (DeMan, Rogosa and Sharpe) MRS culture medium were purchased from Beijing Aoboxing Biotechnology Co., Ltd. (Beijing, China). Lactobacillus plantarum, Lactobacillus reuteri, Lactobacillus rhamnosus, and Pediococcus pentosaceus were obtained from China Microbial Culture Preservation Center (Beijing, China). Pectinase, celluclast and hemicellulase were purchased from Novozymes, Ltd., China. The standard organic acids (tartaric acid, malic acid, lactic acid, citric acid, succinic acid, fumaric acid, and total organic acids) belong to HPLC grade. | CultivationThe strains were activated using the method described by Tang et al. ( 2017) with sight...

Ectoine had important physiological functions and superior potential applications, so the study of ectoine was extensively attented. This article was related to kinetic models of cell growth, product formation and substrate consumption, which was not only established according to the characteristics of ectoine batch fermentation by Halomonas salina DSM 5928 but also obtained the kinetic parameters by the nonlinear fitting method in the Microcal Origin software. Logistic, Luedeking-Piret and Luedeking-Piret-like equations was applied to analyze the cell growth, the ectoine formation and the substrate consumption by the kinetic model，respectively. The results between calculated values and experimental data were coincident. By fitting, correlation coefficients R2 were ≥ 0.989. The fermentation conditions of ectoine were analyzed according to the model. The results showed that ectoine productivity (0.28 g/L/h) was the highest when initial monosodium glutamate concentration (S0) was 60 g/L. However, when S0 was 80 g/L, the ectoine concentration was maximal, i.e., 7.59 g/L. The research suggested that ectoine formation belonged to the mixed kinetic mechanism of cell growth and biomass concentration, while the ectoine production mainly depended on instantaneous biomass concentration. The fermentation method for improving ectoine concentration was further proved. The established kinetic model will be of significant value to provide the optimal conditions of present process.