Proteolytic Activity of Lactic Acid Bacteria and Yeasts Isolated from Commercial and Homemade Kefir Samples

Esin Orhan Yanıkan; Kamuran Ayhan; Serap Coşansu

Proteolytic Activity of Lactic Acid Bacteria and Yeasts Isolated from Commercial and Homemade Kefir Samples

Abstract

The microbiological composition of kefir contributes significantly to its nutritional and functional properties, particularly due to the proteolytic activity of lactic acid bacteria (LAB) and yeasts. This study aimed to isolate and identify proteolytic microorganisms from ten kefir samples, including commercial, homemade, and traditional types, and to assess their ability to hydrolyze milk proteins. A total of 81 isolates were obtained using PCA, MRS, and YGC agar, representing total mesophilic bacteria, LAB, and yeasts, respectively. Proteolytic activity was quantified spectrophotometrically by measuring the release of tyrosine. Results revealed significant variability among isolates, with MRS-derived LAB strains exhibiting the highest proteolytic activity, particularly isolate M21 (191.1 µg/mL). Several YGC isolates also exhibited high enzymatic potential, underscoring the contribution of yeasts and yeast-associated bacteria to kefir fermentation. Biochemical identification confirmed key strains such as Streptococcus thermophilus and Lactococcus lactis subsp. lactis. These findings underscore the significance of kefir-derived microbiota in the development of functional dairy cultures, providing a basis for selecting strains with robust proteolytic capabilities for biotechnological applications.

Keywords

Kefir, Lactic acid bacteria, Proteolytic activity, Fermented milk, Starter cultures

Supporting Institution

Scientific Research Projects Coordination Unit of Ankara University

Project Number

Project Number: 13H4343004.

Thanks

Authors gratefully acknowledge the financial support provided by the Scientific Research Projects Coordination Unit of Ankara University under Project Number 13H4343004.

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Details

Primary Language

English

Subjects

Food Microbiology, Dairy Technology

Journal Section

Research Article

Authors

Esin Orhan Yanıkan
0000-0003-3275-8679
Türkiye

Kamuran Ayhan ^*
0000-0003-4890-8010
Türkiye

Serap Coşansu
0000-0003-2875-1335
Türkiye

Early Pub Date

March 16, 2026

Publication Date

March 16, 2026

Submission Date

December 21, 2025

Acceptance Date

March 5, 2026

Published in Issue

Year 2026 Volume: 1 Number: 1

IZ

https://izlik.org/JA43EN99EE

APA

Orhan Yanıkan, E., Ayhan, K., & Coşansu, S. (2026). Proteolytic Activity of Lactic Acid Bacteria and Yeasts Isolated from Commercial and Homemade Kefir Samples. Food Science Insights, 1(1), 17-26. https://izlik.org/JA43EN99EE

AMA

1.Orhan Yanıkan E, Ayhan K, Coşansu S. Proteolytic Activity of Lactic Acid Bacteria and Yeasts Isolated from Commercial and Homemade Kefir Samples. Food Science Insights. 2026;1(1):17-26. https://izlik.org/JA43EN99EE

Chicago

Orhan Yanıkan, Esin, Kamuran Ayhan, and Serap Coşansu. 2026. “Proteolytic Activity of Lactic Acid Bacteria and Yeasts Isolated from Commercial and Homemade Kefir Samples”. Food Science Insights 1 (1): 17-26. https://izlik.org/JA43EN99EE.

EndNote

Orhan Yanıkan E, Ayhan K, Coşansu S (April 1, 2026) Proteolytic Activity of Lactic Acid Bacteria and Yeasts Isolated from Commercial and Homemade Kefir Samples. Food Science Insights 1 1 17–26.

IEEE

[1]E. Orhan Yanıkan, K. Ayhan, and S. Coşansu, “Proteolytic Activity of Lactic Acid Bacteria and Yeasts Isolated from Commercial and Homemade Kefir Samples”, Food Science Insights, vol. 1, no. 1, pp. 17–26, Apr. 2026, [Online]. Available: https://izlik.org/JA43EN99EE

ISNAD

Orhan Yanıkan, Esin - Ayhan, Kamuran - Coşansu, Serap. “Proteolytic Activity of Lactic Acid Bacteria and Yeasts Isolated from Commercial and Homemade Kefir Samples”. Food Science Insights 1/1 (April 1, 2026): 17-26. https://izlik.org/JA43EN99EE.

JAMA

1.Orhan Yanıkan E, Ayhan K, Coşansu S. Proteolytic Activity of Lactic Acid Bacteria and Yeasts Isolated from Commercial and Homemade Kefir Samples. Food Science Insights. 2026;1:17–26.

MLA

Orhan Yanıkan, Esin, et al. “Proteolytic Activity of Lactic Acid Bacteria and Yeasts Isolated from Commercial and Homemade Kefir Samples”. Food Science Insights, vol. 1, no. 1, Apr. 2026, pp. 17-26, https://izlik.org/JA43EN99EE.

Vancouver

1.Esin Orhan Yanıkan, Kamuran Ayhan, Serap Coşansu. Proteolytic Activity of Lactic Acid Bacteria and Yeasts Isolated from Commercial and Homemade Kefir Samples. Food Science Insights [Internet]. 2026 Apr. 1;1(1):17-26. Available from: https://izlik.org/JA43EN99EE