Microalgae as a source of vitamin K1

Vitamin K1 has recently been identified as a potentially important nutrient for prevention of chronic diseases, especially those associated with aging, like osteoporosis and cardiovascular disease. Currently the majority of Vitamin K1 is produced via chemical synthesis; the aim of this work is to examine the potential to produce Vitamin K1 using microalgae. Biological synthesis produces only the active E-isomer, whereas chemical synthesis produces 10–20% of the inactive Z-isomer. Biosynthesis also utilises mild operating conditions, sustainable production methods, and has the potential to simultaneously produce other beneficial compounds. Seven different species of microalgae were screened; the cyanobacterium Anabaena cylindrica was identified as the richest source of vitamin K1. Concentrations were of the order 200 μg g−1 on a dry-weight basis, which is around six times higher than rich dietary sources such as spinach and parsley; one gram of the algae provides approximately three times the daily adult intake for Vitamin K1. By optimizing the growth conditions (lighting and medium), the productivity was increased fourfold to 22 μg L−1 d−1. Analysis of the nutritional properties of the biomass revealed that it contained high levels of protein (69% (w/w)) and Vitamin B12 (1.5 μg g−1), in addition to the high concentration of phylloquinone. An animal study was performed to evaluate the potential toxicity of the biomass; however, no evidence of acute toxicity was observed even at relatively high addition rates (15% (w/w)). These results support the use of microalgae, specifically A. cylindrica, as a source of phylloquinone.