2023 Volume 79 Issue 25 Article ID: 23-25033
To increase the fertilizer value of wastewater, the culture of purple non-sulfur bacteria (PNSB), known as photosynthetic bacteria, was focused on. The effects of ammonium nitrogen concentration on the growth of PNSB and the production of value-added substances were clarified through culture experiments using artificial culture media and actual wastewater samples. The specific growth rate calculated from the increase in the number of pufM genes in the experiments using the artificial culture medium revealed that growth inhibition caused by ammonia was expressed as an inhibition constant ranging from 0.73 to 1.6 g N/L. In the experiment using actual wastewater samples, the concentrations of carotenoids and 5-aminolevulinic acid, which are value-added substances, were found to increase in response to the growth of PNSB. It was estimated that 2.3 kg of carotenoids and 50 kg of 5-aminolevulinic acid are produced annually by PNSB cultivation in the filtrate of anaerobically digested sludge, and its ammonium nitrogen content is equivalent to about 17 % of the nitrogen required as fertilizer on the scale of Town A. These results suggest that PNSB cultivation using wastewater has the potential to produce value-added liquid fertilizer.
