Recently, the ability of Lactococcus lactis to become non-culturable during late cheese ripening was investigated. The VNC state is a response to different environmental stresses, as the carbohydrate starvation. Thus, the main goal of the present study was to assess the behaviours of this microorganism throughout manufacturing and ripening of model cheeses. Eight commercial starters, constituted of L. lactis subsp. lactis and cremoris, were inoculated in pasteurized milk to produce miniature cheeses, which were ripened and analysed for six months, by both culture-dependent and -independent approach. Based on RT-qPCR, L. lactis was detected in all samples with loads up to log 3 colony forming units (CFU)/g until the sixth month of ripening. On the contrary, traditional analysis on M17 medium, did not always confirmed the presence of culturable cells of L. lactis. Thus, in order to support the hypothesis of the presence of microorganism cells in VNC state, we tried to “resuscitate” them by supplying different carbon sources. Preliminary results highlighted that medium enrichment with high percentage of glucose (2.5%) seemed to stimulate the cells to become culturable again. This attitude seems to be strains dependent. These results add new knowledge to L. lactis dynamic during cheese ripening and corroborate the hypothesis of the NC state for this microorganism. As future prospective, for a more reliable and effective recovery of lactococci in stressed state, the formulation of specific nutritional media will be better investigated.

Lactococcus lactis viability in cheese ripening

RUGGIRELLO, MARIANNA;COCOLIN, Luca Simone;DOLCI, Paola
2015-01-01

Abstract

Recently, the ability of Lactococcus lactis to become non-culturable during late cheese ripening was investigated. The VNC state is a response to different environmental stresses, as the carbohydrate starvation. Thus, the main goal of the present study was to assess the behaviours of this microorganism throughout manufacturing and ripening of model cheeses. Eight commercial starters, constituted of L. lactis subsp. lactis and cremoris, were inoculated in pasteurized milk to produce miniature cheeses, which were ripened and analysed for six months, by both culture-dependent and -independent approach. Based on RT-qPCR, L. lactis was detected in all samples with loads up to log 3 colony forming units (CFU)/g until the sixth month of ripening. On the contrary, traditional analysis on M17 medium, did not always confirmed the presence of culturable cells of L. lactis. Thus, in order to support the hypothesis of the presence of microorganism cells in VNC state, we tried to “resuscitate” them by supplying different carbon sources. Preliminary results highlighted that medium enrichment with high percentage of glucose (2.5%) seemed to stimulate the cells to become culturable again. This attitude seems to be strains dependent. These results add new knowledge to L. lactis dynamic during cheese ripening and corroborate the hypothesis of the NC state for this microorganism. As future prospective, for a more reliable and effective recovery of lactococci in stressed state, the formulation of specific nutritional media will be better investigated.
2015
How Dead is Dead IV
Zurigo
21-22/05/2015
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Lactococcus lactsis, VNC, RNA analysis, revitalization
Marianna, Ruggirello; Luca, Cocolin; Paola, Dolci
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2318/1525593
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