Mg²⁺ improves biomass production from soybean wastewater using purple non-sulfur bacteria

Soybean wastewater was used to generate biomass resource by use of purple non-sulfur bacteria (PNSB). This study investigated the enhancement of PNSB cell accumulation in wastewater by Mg²⁺ under the light-anaerobic condition. Results showed that with the optimal Mg²⁺ dosage of 10mg/L, biomass production was improved by 70% to 3630mg/L, and biomass yield also was improved by 60%. Chemical Oxygen Demand (COD) removal reached above 86% and hydraulic retention time was shortened from 96 to 72hr. The mechanism analysis indicated that Mg²⁺ could promote the content of bacteriochlorophyll in photosynthesis because Mg²⁺ is the bacteriochlorophyll active center, and thus improved adenosine triphosphate (ATP) production. An increase of ATP production enhanced the conversion of organic matter in wastewater into PNSB cell materials (biomass yield) and COD removal, leading to more biomass production. With 10mg/L Mg²⁺, bacteriochlorophyll content and ATP production were improved by 60% and 33% respectively.