Produção de lactobacillus utilizando permeado de soro de leite microfiltrado como substrato

Abstract

The bacteria Lactobacillus plantarum and L. rhamnosus have great commercial value for the food industry due to their potential application in several products. For these microorganisms to be made available as a lactic culture for the food industry, the development of a process for obtaining economically viable biomass is important. Whey is a nutrient-rich dairy by-product and produced in large quantities by the dairy industry. However, because it has a high competing microbial load, its direct application as a culture medium without previous sterilization (autoclaving) prevents its use. However, whey proteins are sensitive to heat and are completely denatured at temperatures from 62.5 ° C and above 70 ° C. This work aimed to evaluate the use of microfiltration in the processing of serum in order to obtain a sterile permeate rich in nutrients for use as a culture medium for the production of Lactobacillus biomass. Two strains were selected (L. plantarum 1115b and L.rhamnosus 1120a) and four microfiltered whey culture media were evaluated in comparison with MRS: integral (SLI), supplemented integral (SLIS), hydrolyzed (SLH), supplemented hydrolyzate (SLHS). A tubular ceramic membrane system with an average pore diameter of 0.2 μm and a total permeation area of 0.02 m2 was used, at a transmembrane pressure of 3 bar and 35 ° C. Integral serum (SI) and alkalase hydrolyzed serum (SH) were microfiltered, and the processes were performed in duplicate. The permeates were characterized according to the content of total and soluble solids, total and reducing sugars, pH, lactic acidity, fat content, protein content, moisture and ash. Supplementation was performed using ammonium sulfate to maintain the same C: N ratio as MRS. After 24h of agitated cultivation at 150 rpm and temperature of 37 ° C, the final concentration of biomass and the sugar content consumed were determined. The permeates showed a good amount of sugars, but low in protein, most of which were retained. The average permeate flows obtained were 80.3 and 80.6 L / hm2 for SI and SH, respectively. The results of the count of total aerobic mesophiles proved the efficiency of microfiltration in the cold sterilization of the permeate. Among the whey-based media, SLHS performed better for strain 1120a and there was no difference between SLH and SLHS for strain 1115b, although the production and yield for both strains were higher in MRS. As the MRS medium is a rich medium composed of other nutrients in addition to the source of carbon and nitrogen, we conclude the need to evaluate the supplementation of the serum with citrate, magnesium, manganese, etc., and also the effect of the concentration of sugars.