Technological characterization of Lactobacillus in semihard artisanal goat cheeses from different Mediterranean areas for potential use as nonstarter lactic acid bacteria

The potential of 25 Lactobacillus isolates from 8 semihard artisanal goat cheeses manufactured in 4 different Mediterranean areas was examined for use as nonstarter lactic acid bacteria. The isolates were identified using 16S rDNA sequence analysis. Sixteen strains belonged to Lactobacillus paracasei and 9 to Lactobacillus rhamnosus. The isolates were first screened for salt tolerance, exopolysaccharide and diacetyl production, proteolytic and lipolytic activity, and acidification and autolyzing capacities. Most of the lactobacilli displayed strong salt tolerance [20 strains, including 13 of Lb. paracasei and 7 of Lb. rhamnosus, could grow at 6% (wt/vol) salt], low acidification activity (16 strains, including 9 of Lb. paracasei and 7 of Lb. rhamnosus, presented change in pH ≤0.4 U after 6 h of growth), and high autolytic activity (14 strains, including 9 of Lb. paracasei and 5 of Lb. rhamnosus, showed autolysis values ranging between 25 and 65%). Eleven Lb. paracasei and 6 Lb. rhamnosus produced exopolysaccharide, whereas 8 Lb. paracasei and 4 Lb. rhamnosus produced diacetyl. Moreover, 9 Lb. paracasei and 6 Lb. rhamnosus showed proteolytic activity; none of the isolates showed lipolytic activity. Based on the above characteristics, 8 strains were further evaluated for peptidase activity, including aminopeptidase, dipeptidyl aminopeptidase, and dipeptidase activities. The results indicated that all strains showed peptidase activity toward selected substrates. The substrate specificity and extent of peptidase activities were strain-dependent. Four strains (A-3, B-4, D-3, and D-8) presented the best characteristics and represented the most promising nonstarter lactic acid bacteria candidates for use in industrial manufacturing of goat cheese.