Characterization of a vitamin B12 compound from unicellular coccolithophorid alga (Pleurochrysis carterae)

The utility of algae as sources of high value nutritional ingredients, particularly for alternative/complementary proteins to improve human health

As the global population continues to grow, the demand for dietary protein is rapidly increasing, necessitating the exploration of sustainable and nutritious protein sources. Algae has emerged as a promising food source due to their high value ingredients such as proteins, as well as for their environmental sustainability and abundance. However, knowledge gaps surrounding dietary recommendations and food applications restrict algae's utilization as a viable protein source. This review aims to address these gaps by assessing the suitability of both microalgae and macroalgae as alternative/complementary protein sources and exploring their potential applications in food products. The first section examines the potential suitability of algae as a major food source by analyzing the composition and bioavailability of key components in algal biomass, including proteins, lipids, dietary fiber, and micronutrients. Secondly, the biological effects of algae, particularly their impact on metabolic health are investigated with an emphasis on available clinical evidence. While evidence reveals protective effects of algae on glucose and lipid homeostasis as well as anti-inflammatory properties, further research is required to understand the longer-term impact of consuming algal protein, protein isolates, and concentrates on metabolic health, including protein metabolism. The review then explores the potential of algal proteins in food applications, including ways to overcome their sensory limitations, such as their dark pigmentation, taste, and odor, in order to improve consumer acceptance. To maximize algae's potential as a valuable protein source in the food sector, future research should prioritize the production of more acceptable algal biomass and explore new advances in food sciences and technology for improved consumer acceptance. Overall, this paper supports the potential utility of algae as a sustainable and healthy ingredient source for widespread use in future food production.

Microalgal assimilation of vitamin B12 toward the production of a superfood

A network of components from different metabolic pathways is the building scaffold of an indispensable compound in the human organism-vitamin B₁₂ . The biosynthesis of this compound is restricted to a limited number of representatives of bacteria and archaea, while vitamin B₁₂ -dependent enzymes are spread through several domains of life. Different attempts have been performed to increase vitamin B₁₂ levels in dietary products, particularly in vegetarian and vegan dietary regimes. The integration of vitamin B₁₂ in microalgae through symbiosis with microorganisms generally recognized as safe, for example the probiotic Lactobacillus reuteri, can even increase the nutritional value of the microalgal biomass. This study reviews the microbial production of vitamin B₁₂ based on genetic analyses and chemical studies. Recent genetic approaches are focused, particularly potential metabolic engineering targets to increase vitamin B₁₂ production. The bioincorporation of vitamin B₁₂ in microalgae as an attempt to provide a superfood is also reviewed. PRACTICAL APPLICATIONS: Novel food habits (i.e., vegan lifestyle) may lack relevant nutrients, including vitamin B₁₂ . Therefore, there is an increased demand for dietary products rich in vitamin B₁₂ . Of potential interest is the provision of microbial-based superfood rich in numerous nutrients, including this vitamin. This manuscript provides an in-depth and timely overview on vitamin B₁₂ biosynthesis and the major advances on metabolic engineering for improved vitamin B₁₂ production by probiotic bacteria and other microorganisms generally recognized as safe. A relevant advance would result from the bioincorporation of vitamin B₁₂ in alternative microorganisms (non-vitamin B₁₂ producers) increasingly recognized as superfood, that is microalgae.

Biologically active vitamin B12 compounds in foods for preventing deficiency among vegetarians and elderly subjects

The usual dietary sources of vitamin B12 are animal-source based foods, including meat, milk, eggs, fish, and shellfish, although a few plant-based foods such as certain types of dried lavers (nori) and mushrooms contain substantial and considerable amounts of vitamin B12, respectively. Unexpectedly, detailed characterization of vitamin B12 compounds in foods reveals the presence of various corrinoids that are inactive in humans. The majority of edible blue-green algae (cyanobacteria) and certain edible shellfish predominately contain an inactive corrinoid known as pseudovitamin B12. Various factors affect the bioactivity of vitamin B12 in foods. For example, vitamin B12 is partially degraded and loses its biological activity during cooking and storage of foods. The intrinsic factor-mediated gastrointestinal absorption system in humans has evolved to selectively absorb active vitamin B12 from naturally occurring vitamin B12 compounds, including its degradation products and inactive corrinoids that are present in daily meal foods. The objective of this review is to present up-to-date information on various factors that can affect the bioactivity of vitamin B12 in foods. To prevent vitamin B12 deficiency in high-risk populations such as vegetarians and elderly subjects, it is necessary to identify plant-source foods that contain high levels of bioactive vitamin B12 and, in conjunction, to prepare the use of crystalline vitamin B12-fortified foods.

Vitamin B12 sources and bioavailability

The usual dietary sources of vitamin B(12) are animal foods, meat, milk, egg, fish, and shellfish. As the intrinsic factor-mediated intestinal absorption system is estimated to be saturated at about 1.5-2.0 microg per meal under physiologic conditions, vitamin B(12) bioavailability significantly decreases with increasing intake of vitamin B(12) per meal. The bioavailability of vitamin B(12) in healthy humans from fish meat, sheep meat, and chicken meat averaged 42%, 56%-89%, and 61%-66%, respectively. Vitamin B(12) in eggs seems to be poorly absorbed (< 9%) relative to other animal food products. In the Dietary Reference Intakes in the United States and Japan, it is assumed that 50% of dietary vitamin B(12) is absorbed by healthy adults with normal gastro-intestinal function. Some plant foods, dried green and purple lavers (nori) contain substantial amounts of vitamin B(12), although other edible algae contained none or only traces of vitamin B(12). Most of the edible blue-green algae (cyanobacteria) used for human supplements predominantly contain pseudovitamin B(12), which is inactive in humans. The edible cyanobacteria are not suitable for use as vitamin B(12) sources, especially in vegans. Fortified breakfast cereals are a particularly valuable source of vitamin B(12) for vegans and elderly people. Production of some vitamin B(12)-enriched vegetables is also being devised.

Purification and characterization of corrinoid-compounds from the dried powder of an edible cyanobacterium, Nostoc commune (Ishikurage)

Vitamin B12 content (98.8 +/- 5.6 microg/100 g dry weight) of an edible cyanobacterium, Nostoc commune (Ishikurage) was determined by the Lactobacillus delbrueckii ATCC 7830 microbiological method. Bioautography with vitamin B12-dependent Escherichia coli 215 indicated that N. commune contained two (main and minor) corrinoid-compounds. These corrinoid-compounds were purified to homogeneity from the dried algal cells and characterized. The main and minor purified corrinoid-compounds were identified as pseudovitamin B12 and vitamin B12, respectively, on the basis of silica gel 60 TLC, C18 reversed-phase HPLC, 1H NMR spectroscopy, and UV-visible spectroscopy. These results suggest that the bacterial cells are not suitable for use as a vitamin B12 source, especially in vegetarians.

Purification and characterization of a corrinoid-compound in an edible cyanobacterium Aphanizomenon flos-aquae as a nutritional supplementary food

The vitamin B12 concentration of the dried cells of Aphanizomenon flos-aquae was determined by both microbiological method with Lactobacillus delbrueckeii ATCC7830 and chemiluminescence method with intrinsic factor. The Aphanizomenon cells contained 616.3 +/- 30.3 micro g (n = 4) of vitamin B12 per 100 g of the dried cells by the microbiological method. The values determined with the chemiluminescence method, however, were only about 5.3% of the values determined by the microbiological method. A corrinoid-compound was purified from the dried cells and characterized. The purified corrinoid-compound was identified as pseudovitamin B12 (an inactive corrinoid-compound for humans) by silica gel 60 TLC, C18 reversed-phase HPLC, ultraviolet-visible spectroscopy, and 1H NMR spectroscopy. The results suggest that the Aphanizomenon cells are not suitable for use as a vitamin B12 source, especially in vegans.

Uptake and physiological function of vitamin B12 in a photosynthetic unicellular coccolithophorid alga, Pleurochrysis carterae

The photosynthetic coccolithophoid alga, Pleurochrysis (Hymenomonas) carterae, could take up and accumulate exogenous vitamin B12, most of which was converted into the coenzyme forms of vitamin B12. Two vitamin B12-dependent enzyme activities (methylmalonyl-CoA mutase, 2.6+/-0.4 nmol/min/mg protein and methionine synthase, 85.1+/-38.9 pmol/min/mg protein) could be found in a cell homogenate of the vitamin B12-supplemented alga. Most of the methylmalonyl-CoA mutase activity and 19.2% of the vitamin B12 accumulated by the algal cells were recovered in the macromolecular fractions with Mr of 150 kDa, although the remaining vitamin B12 was found only in free vitamin B12 fractions.