Significance of Heme-Based Respiration in Meat Spoilage Caused by Leuconostoc gasicomitatum

Abstract

ABSTRACTLeuconostoc gasicomitatumis a psychrotrophic lactic acid bacterium (LAB) which causes spoilage in cold-stored modified-atmosphere-packaged (MAP) meat products. In addition to the fermentative metabolism,L. gasicomitatumis able to respire when exogenous heme and oxygen are available. In this study, we investigated the respiration effects on growth rate, biomass, gene expression, and volatile organic compound (VOC) production in laboratory media and pork loin. The meat samples were evaluated by a sensory panel every second or third day for 29 days. We observed that functional respiration increased the growth (rate and yield) ofL. gasicomitatumin laboratory media with added heme andin situmeat with endogenous heme. Respiration increased enormously (up to 2,600-fold) the accumulation of acetoin and diacetyl, which are buttery off-odor compounds in meat. Our transcriptome analyses showed that the gene expression patterns were quite similar, irrespective of whether respiration was turned off by excluding heme from the medium or mutating thecydBgene, which is essential in the respiratory chain. The respiration-based growth ofL. gasicomitatumin meat was obtained in terms of population development and subsequent development of sensory characteristics. Respiration is thus a key factor explaining whyL. gasicomitatumis so well adapted in high-oxygen packed meat.