Strategies for Adaptive Evolution of Lactic Acid Bacteria for Seabuckthorn Juice Fermentation

Abstract:

[Objective] To enhance the stress resistance of lactic acid bacteria in seabuckthorn juice by inducing the adaptive evolution of the bacteria under the stress of main organic acids. [Method] First, two strains of lactic acid bacteria suitable for fermenting seabuckthorn juice were selected from eight strains isolated from Jiangshui collected from Ningxia. Adaptive evolution was induced under L-malic acid and quinic acid stress, and the two strategies were compared regarding the performance in improving stress resistance of the strains. Subsequently, strain LP-1 was subjected to L-malic acid stress for 125 d. [Result] The fermentation of seabuckthorn juice with the modified strain LP-1-679 showed a lactic acid yield of 0.4 g/L and a malic acid consumption rate of 88.24%, which were 2.67 and 6.60 times those of the original strain, respectively. Moreover, strain LP-1-679 exhibited genetic stability. Compared with the original strain, strain LP-1-679 led to a decrease in the mass fraction of saturated fatty acids (C14:0 and C21:0) and an increase in the mass fraction of unsaturated fatty acids (C16:1, C18:1n9c, and C22:1n9). [Conclusion] A lactic acid bacterial strain with good fermentation performance and strong genetic stability is obtained after acid stress treatment. This strain might resist acid stress by adjusting the composition of fatty acids in the cell membrane.