Growth and metabolite production by mixed-strain starter cultures. [Erratum: 1999, v. 38 (1), p. 187.]

Microbial growth, substrate utilisation and product formation during growth of several mixed-strain mesophilic D-, DL-, and L-type starter cultures in reconstituted skim milk were measured. Non-citrate-utilising lactococci reached levels of ∼9.0 log colony forming units (cfu) per ml in all cultures whereas citrate-utilising lactococci varied from 7.0 to 9.0 log cfu/ml. Maximum numbers of leuconostocs were generally ∼7.0 log cfu/ml. Lactate production reached ∼100 mM and was stoichiometric with lactose utilisation. Citrate was used by all cultures, but more rapidly by D- and DL- type cultures than by L-type cultures. Acetate production reached ∼8 mM and was less than the theoretical expectation. Ethanol was not produced by any culture. Diacetyl and acetoin were produced by all cultures. D and DL cultures produced greater amounts of acetoin (4 mM) than L cultures, which produced 1.5 mM. Similar amounts of diacetyl (0.05 mM) were produced by all cultures, except the D culture, 4/25, which produced 0.3 mM. None of the seven cultures tested produced α-acetolactate, except culture 4/25 which produced ∼2 mM. α-Acetolactate diacetyl and acetoin production peaked when citrate had been completely utilised.