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Lactobacillus reuteri I5007 has well-documented adhesion properties and health benefits. Future industrial use of Lact. reuteri I5007 will require the development of effective fermentation procedures and high bacterial survival following drying. Therefore, this study was conducted to determine the impact of altering fermentation pH and temperature on the fatty acid composition of the bacterial membranes and subsequent survival of Lact. reuteri I5007 following freeze-drying. Initially, a response surface methodology was used to determine the optimal fermentation pH (5·7) and temperature (37°C), with regard to producing the maximum number of Lact. reuteti I5007 cells. However, when subjected to the optimal fermentation pH and temperature (control treatment), the subsequent survival of Lact. reuteri I5007 following freeze-drying was only 12·95%. Growth at a higher temperature (47°C) or at a neutral pH (pH 6·7) significantly increased the survival of Lact. reuteri I5007 following freeze-drying compared with the control. In contrast, an acidic pH (pH 4·7), or cold (27°C) and extremely cold (4°C) temperatures during fermentation significantly reduced Lact. reuteri I5007 survival following freeze-drying. The fatty acid composition of the membranes of Lact. reuteri I5007 was altered by the different fermentation conditions tested. An increase in the ratio of unsaturated fatty acids (UFA) to saturated fatty acids (SFA) in the bacterial membrane was associated with higher survival of Lact. reuteri I5007. In conclusion, it appears that the use of a higher temperature (47°C) or neutral pH (6·7) during fermentation resulted in increased survival of Lact. reuteri I5007 following freeze-drying. Significance and impact of the study: In this study, we found that a higher fermentation temperature or a neutral pH, rather than cold or acidic conditions, leads to increased survival of Lact. reuteri I5007 during subsequent freeze-drying. This finding has important implications for the future industrial production of this probiotic strain., (© 2014 The Society for Applied Microbiology.) more...

Aim: Lactobacillus fermentum is a widely utilized probiotic compound fed as an alternative to antibiotics for growth promotion in a wide variety of livestock species. The objective of this research is to develop an economical and practical fermentation medium for the growth of Lact. fermentum using response surface methodology., Methods and Results: A two-level Plackett-Burman design was used to determine which factors in the fermentation medium influence the growth of Lact. fermentum. Under our experimental conditions, peptone, urea and yeast extract were found to be major factors. Then, the steepest ascent method and the central composite design were applied to optimize the culture of Lact. fermentum. The following composition of the fermentation medium was estimated to be the most economical formula (per litre): 30 g corn syrup, 15 g glucose, 14.4 g peptone, 7 g (NH(4))(2)SO(4), 0.5 g urea, 3 g sodium acetate, 4 g sodium citrate, 0.1 g MnSO(4).4H(2)O, 0.5 g MgSO(4).7H(2)O, 7.3 g yeast extract, 0.5 g K(2)HPO(4)., Conclusion: Based on 10 side-by-side comparisons, we found that the yield of Lact. fermentum using our fermentation medium was 64% greater than those using modified de Man, Rogosa and Sharp broth (MRS) medium (1.8 x 10(9) CFU ml(-1)vs 1.1 x 10(9) CFU ml(-1), respectively), while the cost was 89% lower than MRS. This research indicates that it is possible to increase bacterial yield by using inexpensive materials., Significance and Impact of the Study: It is more likely that the use of Lact. fermentum as a probiotic will increase. The low cost medium developed in this research can be used for large-scale, commercial application where economics are quite likely to be important. more...