Effect of Sea Salt and Taro Waste on Fungal <i>Mortierella alpina</i> Cultivation for Arachidonic Acid-Rich Lipid Production

Arachidonic acid (ARA), an important polyunsaturated fatty acid (PUFA), acts as a precursor for eicosanoid hormones, such as prostaglandins, leukotrienes and other biological substances in human and animal bodies. <i>Mortierella alpina</i> is considered to be a potential strain for ARA production. Using agricultural waste as a substrate for microbial fermentation could achieve biorefinery concepts, and sea water utilization of the cultivation process could help to conserve fresh water resources. The objectives of this study were to find a potential <i>M. alpina</i> strain for ARA production, to investigate the tolerance of salinity and to evaluate the feasibility of the taro waste hydrolysate for <i>M. alpina</i> cultivation. The result showed that <i>M. alpina</i> FU30797 had the highest lipid content (25.97%) and ARA ratio (34.60%) among three strains. Furthermore, there was no significant difference between 0 and 10 g/L of sea salt solution on the biomass concentration and lipid content of <i>M. alpina</i> FU30797. The acidic hydrolysate and enzymatic hydrolysate of taro peel waste (TPW) were both utilized as culture substrates by <i>M. alpina</i> FU30797; however, the substrate up-take rate and lipid content in the TPW enzymatic hydrolysate cultivation were 292.33 mg/L-h and 30.68%, respectively, which are higher than those in acidic hydrolysate cultivation, and the ARA ratio was 33.05% in the enzymatic hydrolysate cultivation. From fed-batch cultivation in the bioreactor, the lipid content and ARA ratio reached 36.97% and 46.04%, respectively. In summary, the results from this project could potentially provide useful information for developing the PUFA-ARA bioprocess by using <i>M. alpina</i>.