Factors Influencing Microbial Oil Production from Food Waste Hydrolysates by Fermentation Using Saccharomyces cerevisiae As2.516
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Abstract:
To increase microbial oil production by fermentation from food waste hydrolysates and to study the characteristics of fermentation production and the factors that influence it, Saccharomyces cerevisiae As2.516 was used as a test strain. Fermentation was conducted in a 1-L fermentor, and the fermentation conditions were as follows: initial amount of food waste hydrolysates, 90% (V/V); agitation speed, 180 r/min; aeration rate, 2.5 L/min; fermentation cycle, 10 d. The fermentation process was affected by the initial pH value, temperature, inoculation biomass, content of reducing sugar, and concentrations of inorganic salts and metal ions. The optimal culture conditions were as follows: pH value, 6; temperature, 30 ℃; inoculum size, 10%. Under these conditions, the maximum biomass, oil production, and product conversion rate were observed. On day 7 of the fermentation by S. cerevisiae, the highest oil yield was attained (4.26 g/L), and the biomass and oil production rate were 12.95 g/L and 32.9%, respectively. The gas chromatography analysis showed that C16 and C18 fatty acids were the main components of the fatty acids produced by fermentation, and unsaturated fatty acids accounted for 72.09%. Inorganic salts were abundant in the food waste hydrolysates; additional potassium, magnesium, manganese, and other ions could inhibit bacterial growth and affect oil production. Therefore, except for a trace amount of CuSO4?5H2O (1 × 10-4 g/L), it was not necessary to add additional inorganic salts. S. cerevisiae , which used food waste hydrolysates, was characterized as broad-spectrum and stress tolerant.
