PROTEIN CAPABILITY OF STARTING-DOUGHS LACTIC-ACID BACTERIA

Protein degrading capabilities of pure strains of homofermentative - Lactobacillus plantarum, Enterococcus faecium - and heterofermentative - Lactobacillus brevis - starting-doughs lactic acid bacteria, have been investigated in unfermented and fermented dough samples by comparing electrophoretic patterns and densitometer profiles. Accumulation of polypeptide (3,500-25,000 D) and peptidization of protein subunits (27,500-80,000 D) took place in fermented doughs at different rates depending on the lactic acid bacteria starting fermentation. Under dissociating electrophoretic conditions polypeptide subunits of 8,000 D (L. brevis, L. plantarum) and 15,000 D (L. brevis, L. plantarum, E. faecium) were generated from 4 to 24 hours of fermentation. Under electrophoretic reducing conditions, protein subunits of 25,000, 37,000, 58.000, 67.000 and 80,000 daltons were detected up to 4 hours of fermentation in all doughs. Progressive proteolytic action along fermentation on soluble polypeptides and proteins, decreased the amount of subunits of 11,000, 65,000 (L. brevis, L. plantarum, E. faecium) and 14,000 D (L. plantarum, E. faecium). Specific degradation of non soluble proteins and higher molecular weight soluble fragments was evidenced by the subunits of 15,000 and 35,000 D. The later subunits increased to 4 hour-fermentation for doughs containing lactobacilli, and from 4 to 24 hours for E. faecium starting doughs. At prolonged periods of fermentation (24 hours), level of subunits of 27,000 and 37,000 daltons (E. faecium) and 8,000 daltons (L. brevis, L. plantarum) sharply increased.