Optimization of culture conditions for kefiran production in whey: The structural and biocidal properties of the resulting polysaccharide

Abstract

In this study, the culture conditions necessary for the effective production of kefiran, using whey as a substrate, were evaluated through the one-factor-at-a-time and central-composite design methods. Using the optimal factors (whey supplemented with 15% (w/v) glucose fermented at 30 °C for 10 h without shaking), 0.20 g L−1 h−1 kefir grains composed of 18.57% (w/w) kefiran was obtained. The resulting polysaccharide was analyzed by high-pressure size-exclusion chromatography, gas chromatography-mass spectrometry, nuclear magnetic resonance, Fourier-transform infrared and Raman spectroscopy. Altogether, the results indicated that the purified polymer was homogenous and composed of galactose and glucose. The biocidal properties of the resulting kefiran were assessed, for the first time, using Live/Dead BacLight® real-time analysis, which indicated antimicrobial activity against Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus, and Salmonella typhimurium strains. Additionally, the kefiran, when applied to various S. typhimurium strains, showed diverse biocidal results when in the presence of antibiotic multiresistance markers. In summary, these results demonstrated that kefiran can be produced from whey-supplemented media with high productivity and without losing its structural or biocidal properties.