Metabolic engineering of thermophilic Bacillus methanolicus for riboflavin overproduction from methanol.

The growing need of next generation feedstocks for biotechnology spurs an intensification of research on the utilization of methanol as carbon and energy source for biotechnological processes. In this paper, we introduced the methanol-based overproduction of riboflavin into metabolically engineered Bacillus methanolicus MGA3. First, we showed that B. methanolicus naturally produces small amounts of riboflavin. Then, we created B. methanolicus strains overexpressing either homologous or heterologous gene clusters encoding the riboflavin biosynthesis pathway, resulting in riboflavin overproduction. Our results revealed that the supplementation of growth media with sublethal levels of chloramphenicol contributes to a higher plasmid-based riboflavin production titre, presumably due to an increase in plasmid copy number and thus biosynthetic gene dosage. Based on this, we proved that riboflavin production can be increased by exchanging a low copy number plasmid with a high copy number plasmid leading to a final riboflavin titre of about 523 mg L-1 in methanol fed-batch fermentation. The findings of this study showcase the potential of B. methanolicus as a promising host for methanol-based overproduction of extracellular riboflavin and serve as basis for metabolic engineering of next generations of riboflavin overproducing strains.

[Health-promoting properties of pectin]. / Prozdrowotne wlasciwosci pektyn.

Pectin, a heteropolysaccharide commercially derived from the cell wall of higher plants, is mainly used in food as a gelling agent in jams and jellies as well as a stabilizer in fruit juice and milk drinks. It has also received great interest as a source of dietary fiber. Furthermore, pectin is proved to have diverse biological activities including lipid and cholesterol level lowering effects, serum glucose and insulin content lowering effects, gastric emptying delay, and anti-cancer activities. Pectin and pectic oligosaccharides have been shown to induce apoptosis in human colonic adenocarcinoma cells and to have anti-metastatic properties. Dietary pectin can bind metal ions, particularly lead ions, thus reducing their retention in the body and diminishing their toxic effects. On the other hand, pectin enhances intestinal solubility and absorption of ferric iron. Pectin with a low degree of esterification or having a large volume of linear oligogalacturonide segments shows significant mucoadhesion capacity in the gastrointestinal tract. In this way pectin forms a physical barrier protecting epithelium against opportunistic microbial invasion during stress.