Selection of Microorganisms Producing Vitamin B12 from Local (saudi) Isolates@@@انتقاء الكائنات الحية الدقيقة المنتجة لفيتامين ب12 من عزلات محلية (السعودية)

Forty-six bacterial strains were highly varied in their effici~ncy to produce cell biomass and vitamin B12. Propionibacterium freudenreichii ATCC 6207 and two local bacterial isolates (Streptomyces 5184 and Methylomonas methanica 14B-16 were the most efficient strains. Productivity of vitamin BI2 was affected by culturing methods (shake and static), and growth phases.T he highest Vitamin B 12p roductivity waso bserved in shake culture of P. freudenreichii (170.2 1Lg/100m l culture and 68.1ILgl/100 mg biomass dry wt.). This strain also showed a positive correlation between the amount of vitamin and elapsing of time. Other bacterial strains gave amounts of Vito B12r anging from 9.12 to 35.6 1Lg/100m l culture and from 1.19 to 43.6 1Lg/100m l dry wt. biomass. The most efficient strains also showed a high productivity at early stage of growth in shake culture.