Technological and molecular profiling of lactic flora in Hamra ewe's milk cheese from the Algerian steppe.

Abstract

This study explores the technological and functional characteristics of indigenous lactic acid bacteria (LAB) isolated from Hamra ewe’s milk cheese, a traditional semi-refined product from the steppe region of western Algeria. The objective was to identify, characterize, and evaluate the acidifying, proteolytic, and texturizing potential of dominant LAB species contributing to cheese typicity. Thirty-two isolates were obtained and screened using morphological, biochemical, and molecular (multiplex PCR and 16 S rRNA sequencing) methods. Four dominant species were identified: Lactococcus lactis, L. lactis subsp. lactis biovar diacetylactis, Enterococcus faecium, and Lactobacillus acidophilus. Acidification assays revealed that Lactococcus strains were the most active acidifiers, producing 11 to 12.8 g/L of lactic acid with final pH values between 4.17 and 4.36 after 24 h. E. faecium exhibited moderate acidification (9.7 g/L; pH 4.42), while L. acidophilus produced lower acidity (7.2 g/L; pH 4.81). Growth and tolerance tests confirmed adaptation to wide temperature (6 to 55 °C), pH (2.3 to 7.3), and NaCl (1 to 6%) ranges. Coagulation and proteolytic tests indicated that Lactococcus strains ensured rapid milk coagulation (12 h; viscosity 810–980 cP), whereas E. faecium and L. acidophilus displayed notable proteolytic activity, forming lysis zones of 7 to 14 mm. L. acidophilus also produced exopolysaccharides (up to 7.2 g/L on day 10), enhancing texture and firmness. The coordinated microbial succession during fermentation and ripening confirmed the technological potential of these indigenous LAB. Their use as natural starter or adjunct cultures can enhance the sensory quality, authenticity, and typicity of traditional Algerian ewe’s milk cheeses.