Glucose fermentation in the presence of linoleic, oleic and stearic acids by a mixed culture

Long Chain Fatty Acid (LCFA) mixtures containing linoleic, oleic and stearic acids plus carbohydrates are found in a variety of effluents arising from fried food manufacture and milk processing. Accumulation of Volatile Fatty acids (VFAs) due to the presence of LCFAs may impair the operation of an anaerobic system treating effluents containing a mixture of triglycerides and carbohydrates. In this study, the effects of linoleic (C18:2), oleic (C18:1), and stearic (C18:0) acids on glucose fermentation were investigated at 21degreesC using a culture acclimated to glucose. In cultures receiving greater than or equal to300mg dm(-3) LCFAs, residual amounts of glucose remained after approximately 8 h and none was detected after 24 h. Acetate degradation was inhibited in the presence of 300 or more mg dm(-3) linoleic acid (LA), oleic acid (OA), or stearic acid (SA) with more acetate accumulation observed in cultures receiving LA. In comparison to the controls, similar amounts of propionate accumulation were observed in cultures receiving greater than or equal to100 mg dm(-3) of each LCFA. However, in cultures receiving greater than or equal to300 mg dm(-3) LCFAs, more propionate accumulated with complete removal observed within 20 days for only those cultures receiving oleic or stearic acids. Butyrate accumulation was observed only in cultures receiving greater than or equal to300 mg dm(-3) LA and none was detected after 10 days of incubation. (C) 2004 Society of Chemical Industry.