Effects of the ratio of carbon to nitrogen concentration on lipid production by bacterial consortium of sewage sludge using food wastewater as a carbon source

Food wastewater (FWW) and sewage sludge (SS) were used to control the C:N ratio in cultures as a method to increase lipid production by microbial species in SS. FWW and SS were mixed in volumetric ratios (FWW: SS) of 5: 0 (F5), 4: 1 (F4), or 3: 2 (F3). Compared to raw SS, total lipid content production was increased by 263% in F5, 142% in F4, and 111% in F3. These results were caused by increases in the concentrations of triglycerides (TAGs) during lipid enhancement. The fatty acid methyl ester content of TAGs (wt% of extract) was 25.3 in F5, 20.2 in F4 and 13.25 in F3; these were significant improvements over biodiesel production using raw SS. C16:0 fatty acid was mostly converted to C18:1 fatty acid; this is an important result because the proportion of C18:1 strongly influences the quality of biodiesel. This is the first effort to produce biodiesel using FWW instead of synthetic medium as a carbon source. Hence, this study provides a useful solution for treating organic wastes (SS and FWW) simultaneously; this strategy may be an economically viable method for producing biodiesel from organic wastes.