Utilization of saline and viscous food-processing liquid waste for cultivation of thraustochytrid for production of polyunsaturated fatty acids

Biological treatment of saline and viscous food waste is hindered because of the overly concentrated substrates and contaminative growth. To address this issue, the salinity-tolerant Aurantiochytrium sp. L3W was cultivated on saline and viscous yakisoba (Y) and okonomiyaki (O) liquid food wastes supplied by a sauce factory in Hiroshima (Japan) at various viscosities to produce polyunsaturated fatty acids (PUFAs). The salinity of the growth medium may reduce the contaminative growth under non-sterile conditions. It was found that an increased viscosity of 1.34 Pa·s inhibited the growth of strain L3W. The liquid waste samples were diluted to retrieve the effective biomass growth. Cultivation in 25-times-diluted samples at the original acidic pH under non-sterile conditions revealed the docosahexaenoic acid (DHA) levels of 50 mg/g (Y) and 55 mg/g (O). Despite non-sterile conditions, neutral pH 7 adjustment induced a remarkable PUFA production. The resultant biomass, collected from the 25-times-diluted liquid waste samples, contained DHA and eicosapentaenoic acid (EPA) of 105 and 0.11 mg/g (Y); and of 50 and 0.06 mg/g (O), respectively. Furthermore, in the context of carbon and nitrogen consumption, the biomass yield analysis indicated that the sample Y contained more suitable nitrogen for the strain L3W as compared to the control medium. These results confirmed that Y and O samples can be utilized for the cultivation of strain L3W under non-sterile conditions to ultimately produce DHA and EPA. Graphical abstract: [Figure not available: see fulltext.].