Suitability of whey and buttermilk for the growth and frozen storage of probiotic lactobacilli

The growth of six probiotic commercial strains of lactobacilli was assessed in reconstituted dried whey and buttermilk supplemented with yeast extract, meat peptone, soy peptone, tryptone or casein acid hydrolysate at 0.3%, 0.6% or 1%. The addition of 1% glucose was also tested. Growth and acidification kinetics were determined at 37 degrees C using MRS broth and a commercial culture medium as references. The suitability of whey and buttermilk as cryoprotectants at -20 degrees C and -70 degrees C was also assessed. Whey and buttermilk with 0.3% yeast extract were chosen for the growth of probiotic lactobacilli, since no satisfactory growth was observed without an external nitrogen source, whereas glucose did not improve the growth of any of the strains assayed. In general, buttermilk performed as satisfactorily as the reference media. The effectiveness of these media as cryoprotectants was strain dependent: skimmed milk and whey were the most suitable ones, especially for long-term storage at -20 degrees C. However, at -70 degrees C, no significant differences were observed between the culture media assessed. The use of whey or buttermilk as culture media for the production of probiotic lactic acid bacteria and for their cryopreservation implies a novel use of these low-cost products, offering an alternative way of utilizing the by-products of the dairy industry, helping to minimize their negative impact on the environment.