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.