Lactobacillus delbrueckii subsp. bulgaricus F17 and Leuconostoc lactis H52 supernatant delay the decay of strawberry fruits; a microbiome perspective
Strawberries are vulnerable to physical injuries and microbial invasion. To explore if beneficial lactic acid bacteria can improve the shelf life and edible quality of postharvest strawberry fruits, the effects of Lactobacillus F17 and Leuconostoc lactics H52 inoculation on strawberry microbial community structure and saleable characteristics were examined. Lactobacillus delbrueckii subsp. bulgaricus F17 and Leuconostoc lactics H52 isolated from the traditional fermented yak milk in the Qinghai-Tibetan Plateau were used as the potential probiotic inocula. Samples from treated strawberries stored at 25 °C for 0, 12, 24, 48, and 72 hours were analyzed for pH, weight loss percentage, decay percentage, total soluble solids content (SSC) and microbial counts, as well as for microbiome community diversity and canonical correspondence analysis. The results showed that F17 and H52 did not only significantly reduce the weight loss and decay percentage of strawberry fruits, but also delayed the decrease of total SSC and pH (P < 0.05). In addition, F17 and H52 significantly inhibited growth and colonization of aerobic mesophilic bacteria, yeast and mold as well as coliform bacteria. In particularly, by comparing the microbiota composition of the samples, F17 significantly inhibited Pantoea, Mycospherella, Unclassified_fungi and Unclassified_Pleosporales at genus level, whereas H52 inhibited Bacillus, Streptophyta, Mycospherella, Podosphaera and Unclassified_fungi. Moreover, analysis of alpha and beta diversity revealed that F17 and H52 had significantly more inhibitory effect on bacterial species than fungi. The results of canonical correspondence analysis revealed that total SSC and pH were positively correlated with bacteria, whereas decay percentage, weight loss percentage and total SSC were positively associated with fungi. Additionally, Rhodotorula, Hanseniaspora and Rhizopus were positively correlated with strawberry fruits decay and weight loss rate. As a general result, Lactobacillus F17 and Leuconostoc lactics H52 have the potential to promote biological preservation, which is economically important to reduce the loss of strawberry spoilage.