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Aroma formation in retentostat co-cultures of Lactococcus lactis and Leuconostoc mesenteroides

van Mastrigt, Oscar, Egas, Reinier A., Abee, Tjakko, Smid, Eddy J.
Food microbiology 2019 v.82 pp. 151-159
Lactococcus lactis subsp. lactis bv. diacetylactis, Leuconostoc lactis, Leuconostoc mesenteroides, adenosine triphosphate, biomass production, cheesemaking, cheeses, coculture, dietary supplements, dynamic models, lactic acid bacteria, odor compounds, odors, prediction
Lactococcus lactis subsp. lactis biovar diacetylactis and Leuconostoc mesenteroides are considered to be the main aroma producers in Dutch-type cheeses. Both species of lactic acid bacteria were grown in retentostat mono- and co-cultures to investigate their interaction at near-zero growth rates and to determine if co-cultivation enhances the aroma complexity compared to single species performance. During retentostat mono-cultures, the growth rates of both species decreased to less than 0.001 h−1 and a large fraction of the cells became viable but not culturable. Compared to Lc. mesenteroides, L. lactis reached a 3.4-fold higher biomass concentration caused by i) a higher ATP yield on substrate, ii) a higher biomass yield on ATP and iii) a lower maintenance requirement (mATP). Dynamic models estimated that the mATP of both species decreased approximately 7-fold at near-zero growth rates compared to high growth rates. Extension of these models by assuming equal substrate distribution resulted in excellent prediction of the biomass accumulation in retentostat co-cultures with L. lactis dominating (100:1) as observed in ripened cheese. Despite its low abundance (∼1%), Lc. mesenteroides contributed to aroma production in co-cultures as indicated by the presence of all 5 specific Lc. mesenteroides compounds. This study provides insights in the production of cheese aroma compounds outside the cheese matrix by co-cultures of L. lactis and Lc. mesenteroides, which could be used as food supplements in dairy or non-dairy products.