Data Sheet 4_Investigating the survival mechanisms of Lactiplantibacillus plantarum QZW5 under repeated freeze–thaw stress: an integrated study using biochemical assays, environmental cryo-electron microscopy, and multi-omics approaches.xlsx

Introduction<p>Repeated freeze–thaw cycles represent a critical stress factor in frozen food processing, leading to a significant decline in the survival and fermentation performance of lactic acid bacteria.</p>Methods<p>This study investigated the tolerance mechanism of Lactiplantibacillus plantarum QZW5, a resistant strain, after 10 cycles of alternating freezing (−20 °C) and thawing (20 °C). An integrated approach combining physiological and biochemical assays, environmental cryo-electron microscopy, multi-omics analysis, and qPCR validation was employed.</p>Results and Discussion<p>The results showed after freeze–thaw treatment, QZW5 retained an 85.20%survival rate with a 14.80% reduction in growth rate, accompanied by gradual fermentation pH decline.

Its antibacterial activity decreased markedly; for example, the inhibition zone against Micrococcus luteus decreased from 20.36 ± 1.77 mm to 10.64 ± 0.10 mm (≈48% reduction),and ampicillin susceptibility increased by around 18% (inhibition zone from 24.76 ± 0.35 mm to 29.11 ± 0.17 mm),while its biofilm-forming capacity remained stable with OD₅₇₀ values of 1.90 ± 0.23 (CK) and 1.98 ± 0.19 (FT, p > 0.05). Morphological alterations included serrated cell edges and intracellular granule deposition.