Microalgae as a source of vitamin K-1

Vitamin K-1 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 K-1 is produced via chemical synthesis; the aim of this work is to examine the potential to produce Vitamin K-1 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 K-1. Concentrations were of the order 200 mu 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 K-1. By optimizing the growth conditions (lighting and medium), the productivity was increased fourfold to 22 mu gL(-1) d(-1). Analysis of the nutritional properties of the biomass revealed that it contained high levels of protein (69% (w/w)) and Vitamin B-12 (1.5 mu g 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.