Optimisation of vitamin B12 and folate production by Propionibacterium freudenreichii strains in kefir

Vitamin B-12 and folate deficiencies in poor Southern African communities lead to mandatory fortification of basic foodstuffs. Since folate- and B-12-enriched kefir offers a cheaper alternative, regimes to include Propionibacterium freudenreichii (PAB) strains into kefir grains (KG) were investigated: two levels of PAB cell concentrations; freeze-drying KG to preserve PAB activity; and repeated PAB culture additions. Elevated B-12 and folate levels and PCR results confirmed inclusion of PAB in all KG. Repeated inoculations with freeze-dried cultures (PAB concentration 1 x 10(8) cfu mL(-1)) delivered the highest B-12 and folate production rate and concentration after 3 d. The best treatment (freeze-dried inoculum (5 x 10(7) PAB cfu mL(-1)) reacted once, followed by freeze-drying) delivered 186% Recommended Dietary Allowance (RDA) (B-12) and 19% RDA (folate) per 200 mL serving. Freeze-drying preserved PAB activity in KG. (C) 2010 Elsevier Ltd. All rights reserved.