Produção de biomassa de Lactobacillus para obtenção de fermento lático a ser empregado no processamento de queijo de coalho

Abstract

Coalho cheese is a typical variety from the Northeast of the country, but its production is usually handcrafted and faces problems with sanitary quality. Brazilian legislation establishes that cheese-making milk is subjected to the pasteurization process, which destroys, in addition to undesirable bacteria, another important group in cheese making, lactic acid bacteria (BAL). The BALs have been selected from Coalho cheese produced with raw milk for the elaboration of a lactic ferment, which can be used in the cheese making process with pasteurized milk. The general objective of this work was to produce biomass of three bacteria of the genus Lactobacillus, previously characterized with potential for the production of rennet cheese, in a fermenter scale, in order to expand its scale of production. Three strains of Lactobacillus were used, two of Lactobacillus rhamnosus (strains 1057a and 1120a) and one of Lactobacillus plantarum (1115b), grown in fermenter under different conditions of pH, agitation, aeration and culture media. These bacteria were isolated from artisanal Cranberry cheeses produced with raw milk and are deposited in the Collection of Microorganisms of Interest for Embrapa Tropical Agroindustry, stored at -80°C. The parameters analyzed were viable cell counts, determination of the biomass concentration (g/L) at 0, 18, 24, 42 and 48 hours and residual sugar analysis. Shaker biomass production of strains 1120a, 1057a and 1115b were 3,1 g/L, 3,2 g/L and 1,9 g/L, respectively, after 48 hours of fermentation. Strain 1120a produced the highest concentration of biomass in bioreactor (3,2 g/L) when the fermentation was conducted in MRS medium, agitation of 150 rpm without baffles, temperature of 37°C and aeration of 1 v.v.m on the surface of the medium. When the MRS medium was replaced with simplified MRS, biomass production was only 0,7 g/L. PH also influenced biomass production, which was 1,0 g/L for strain 1120a grown at pH 4,7 and 1,1 g/L for strain 1115b at pH 5,7. Strain 1057a produced a biomass of 1,9 g/L at pH 5,7 exhibiting the best performance in the simplified MRS medium.