Kefir Grain Biomass Production: Influence of Different Culturing Conditions and Examination of Growth Kinetic Models

Abstract

In this study, kefir grain biomass growth was investigated in whey enriched with some additives such as yoghurt, milk, glucose, sucrose, yeast extract and carob extract. The fermentation experiments were carried out at 27°C for 10 days by refreshing the cultivation media at the end of each 24 h fermentation period. Maximum and minimum biomass increases were obtained as 1,438 and 836% in whey enriched with 5% (w/v) yeast extract and 10% (v/v) carob extract, respectively. Kefir biomass increase and fermentation kinetics were examined at different temperatures (17, 27, 37°C) and different initial kefir grain concentrations (2.5, 5, 7.5%) for selected culture mediums (in whey and in whey enriched with milk and yoghurt). Optimum temperature and initial grain concentration for kefir biomass growth were obtained as 27°C and 5% for all examined mediums. Modelling studies were performed and various kinetic models tested to represent the kefir biomass growth and fermentation kinetics. The convenience of the kefir biomass growth to the Monod kinetics was also examined. Practical Applications The varied microbial composition of kefir grains provides novel applications to them, such as, in bread production as baker's yeast, cheese production, polysaccharide production, volatile aroma compound production and ethanol production. The biomass increase of kefir grains by traditional inoculation in milk is relatively low, hence to use kefir grains in commercial applications their production has to be improved using alternative cultivation mediums and optimizing the process conditions. So in the study presented by this article the kinetics of kefir grain biomass growth was investigated in whey (an alternative raw material for kefir biomass production that is a dairy liquid waste of negligible cost) enriched with additives such as yoghurt, milk, glucose, sucrose, yeast extract and carob extract to improve the biomass production of kefir and use the whey as an effective low cost substrate. Also the effect of temperature and initial kefir grain concentration on biomass production and fermentation were examined and different mathematical models were analyzed to represent the kefir biomass growth and kefir fermentation kinetics.

Goat milk Kefir with ACE inhibitory activity: Preparation and storage stability evaluation

“…Apar studied the effects of temperature and initial Kefir concentration on biomass production and fermentation. The results showed that the optimal temperature for growth of Kefir biomass and the initial Kefir particle concentration were 27°C and 5%, respectively (Apar, Demirhan, Özel, & Özbek, ). Bensmira studied the effects of fermentation conditions and homogenization pressure on Kefir rheology (Bensmira, Nsabimana, & Jiang, ).…”

Bioremoval of reactive dye Remazol Navy by kefir grains

“…The removal of the dyes by living and inactivated grains drastically decreased to 11.38% and 1.03% as pH was increased to 8. Kefir is an acidic, viscous, lightly carbonated dairy beverage and it is known that the living kefir grains are stable in a wide pH range, since during the fermentation the pH of the milk decrease from 6.8 up to 3.3 [30]. As the decrease in dye removal efficiency was also observed with nonliving kefir grains it can be stated that these decrease is not related with the inactivation of the active microflora of kefir grains.…”

“…The kefir grains (starter culture for the probiotic fermented milk drink kefir) are small, gelatinous white/ yellow irregularly shaped masses consist of live bacteria (lactic acid bacteria of the genus Lactobacillus, Lactococcus, Leuconostoc and acetic acid bacteria) and yeasts (consist of Kluyveromyces, Candida, Saccharomyces and Pichia) in a slimy polysaccharide matrix and are responsible for lactic acid and alcoholic fermentation. Traditional production of kefir drink involves inoculation of milk with a variable amount of grains and fermentation [30,31]. During the fermentation kefir grains increases and in a few day the amount get excess for a specified amount of beverage production and require to remove the excess amount in order to standardization of the product.…”

“…During the fermentation kefir grains increases and in a few day the amount get excess for a specified amount of beverage production and require to remove the excess amount in order to standardization of the product. For instance, the kefir biomass increase was reported as 1294% and 1226% for 10 day consecutive fermentation in 100 ml milk and whey respectively [30]. Whey is a dairy liquid waste which is produced in large quantities throughout the world.…”

“…Production of kefir-like whey beverages has been reported in several works. Hence whey can be used to produce kefir grains, so it can be converted to added value products while the kefir grains are produced cheaply [30,32]. As a result, as a side product (or waste) the excess amount of kefir biomass obtained from milk or whey fermentation can be evaluated in different areas.…”