Biochemical Identification and Characterization of DNA Groups within the Proteus vulgaris Complex

We placed 43 isolates belonging to the Proteus vulgaris complex into proposed DNA groups (genomovars) using five previously recommended tests (tests for esculin hydrolysis, production of acid from salicin, l-rhamnose fermentation, and elaboration of DNase and lipase). On the basis of the results of these five tests, 49% of the isolates fell into DNA groups 5 and 6, 37% fell into DNA group 2, and the remaining 14% fell into DNA groups 3 and 4. Sequencing of the 16S rRNA genes of 11 members of DNA groups 5 and 6 indicated that 10 of these isolates (91%) could be unambiguously assigned to one of these two genomospecies. Overall expression of selected enzymatic and virulence-associated characteristics did not differ significantly among DNA groups

Isolation of a novel Pseudomonas species SP2 producing vitamin B-12 under aerobic condition

Vitamin B-12 is a complex biomolecule that acts as a cofactor for a variety of enzymes in microbial metabolism. Pseudomonas denitrificans is exclusively used as an industrial strain for the production of vitamin B-12 under aerobic conditions. However, only a few strains of Pseudomonas have been reported to possess the capability of producing this vitamin and they are strongly patent-protected. To improve the applicability of the vitamin B-12-producing microorganisms, a new isolate was obtained from municipal waste samples and characterized for its biological properties. The new isolate, designated as SP2, was identified to be a Pseudomonas species based on the sequence homology of its 16S rDNA. Pseudomonas species SP2 had essential genes for vitamin B-12 synthesis such as cobB and cobQ and produced a similar amount of vitamin B-12 (10.6 +/- 0.05 mu g/mL) as P. denitrificans ATCC 13867 in 24 h flask culture. SP2 grew well under aerobic condition with the maximum specific growth rate (A mu (max) ) of 0.91 +/- 0.03/h, but showed a poor growth under micro-aerobic conditions. SP2 was resistant to antibiotics like streptomycin, carbenicillin, ampicillin, cefpodoxime, colistin, nalidixic acid and sparfloxacin. The ability of SP2 to grow faster and produce vitamin B-12 under aerobic conditions makes it a promising host for the production of some biochemicals requiring a coenzyme B-12-dependent enzyme, such as glycerol dehydratase

Vitamin B12 : physiology, production and application

Cobalamin or B12 is an important group of water‐soluble compounds belonging to the cobalt corrinoid family. This chapter provides an overview of B12 chemistry and physical properties, its occurrence in natural sources and quantification of B12, mainly in foods. A summary of key nutritional aspects of B12 in humans is also given, that is, absorption and uptake, metabolic cofactor functions and the current context of B12 deficiencies and their detection, with references to detailed reviews. The chapter presents the current state of B12 production by Propionibacterium and Pseudomonas, including genetic engineering of producing strains, downstream processing (DSP) of fermentation products, B12 purification and future directions for industrial B12 production. Future demand for B12 will likely continue to increase in both developed and developing countries, mainly due to increases in human and animal populations and the ageing population with higher needs for B12‐fortified food