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Biologically Active Vitamin B12 from Edible Seaweeds
Published in Gokare A. Ravishankar, Ranga Rao Ambati, Handbook of Algal Technologies and Phytochemicals, 2019
Tomohiro Bito, Fei Teng, Fumio Watanabe
B12 is synthesized by certain bacteria and archaea only and not by the majority of plants. B12 accumulates in animal tissues from the food chain (Watanabe and Bito 2018). Thus, animal-based, but not plant-based, foods are considered to be a major dietary B12 source (Watanabe 2007). Thus, strict vegetarians or vegans who do not consume any animal-based foods are reportedly at a greater risk of developing B12 deficiency (Pawlak et al. 2013). We have identified edible seaweeds that naturally contain large B12 amounts (Watanabe et al. 2002, 2014). However, some algae have been shown to contain inactive corrinoid compounds, such as pseudovitamin B12 (PseudoB12) (Figure 11.1) (Watanabe et al. 1999a, 2006, Miyamoto et al. 2006). This chapter summarizes the characterization and bioavailability of B12 compounds from edible seaweeds.
Inorganic Chemical Pollutants
Published in William J. Rea, Kalpana D. Patel, Reversibility of Chronic Disease and Hypersensitivity, Volume 4, 2017
William J. Rea, Kalpana D. Patel
MeHg is a potent neurotoxin produced in natural environments from inorganic mercury by anaerobic bacteria. However, until now, the genes and proteins involved have remained unidentified. Parks et al.550 report a two-gene cluster, hgcA and hgcB, required for mercury methylation by Desulfovibrio desulfuricans ND132 and Geobacter sulfurreducens PCA. In either bacterium, deletion of hgcA, hgcB, or both genes abolishes mercury methylation. The genes encode a putative corrinoid protein, HgcA, and a 2 (4Fe-4S) ferredoxin, HgcB, consistent with roles as a methyl carrier and an electron donor required for corrinoid cofactor reduction, respectively. Among bacteria and archaea with sequenced genomes, gene orthologs are present in confirmed methylators but absent in nonmethylators, suggesting a common mercury methylation pathway in all methylating bacteria and archaea sequenced to date.
Oral vitamin B12 supplement is delivered to the distal gut, altering the corrinoid profile and selectively depleting Bacteroides in C57BL/6 mice
Published in Gut Microbes, 2019
Caleb J Kelly, Erica E Alexeev, Linda Farb, Thad W Vickery, Leon Zheng, Campbell Eric L, David A Kitzenberg, Kayla D Battista, Douglas J Kominsky, Charles E Robertson, Daniel N Frank, Sally P Stabler, Sean P Colgan
To our knowledge, this is the first study to profile corrinoids in the distal gut of mice since the LC/MS method was originally described by Allan and Stabler.5 Importantly, it demonstrates that active B12 is a minor constituent of the fecal corrinoid pool in mice (0.44%, 59 ng/g stool) which is similar to published results from human feces (1.4%, 19 ng/g stool).5 We show that oral B12 supplementation in mice, at a level corresponding to human consumption of a 5 mg daily supplement, increased B12 in the distal gut >130 fold. B12 supplementation decreased the absolute concentration of several non-B12 corrinoids. Cobinamide was increased in fecal contents which indicates microbial modification of cobalamin salvaging the corrin ring. Given the ability of microbes to sense and acquire B12,3,9 this likely reflects negative regulation of microbial corrinoid synthesis in the setting of environmental excess.