Heavy metal impact on lipid production from oleaginous microorganism cultivated with wastewater sludge

Using municipal wastewater sludge to produce microbial lipid is an effective way of resource recycling. Sludge contains heavy metals and may lead to negative impact on lipid production. However, relative study has not been reported. In this study, metal impact on Lipomyces starkeyi lipid accumulation was conducted. Results showed that Cd²⁺ had great impact on lipid accumulation, but other metals had no much impact. The maximum lipid content of L. starkeyi cultivated in 0.55 mg/L of Cd²⁺ was only 41% w/w, which was lower than the control (51% w/w). The inhibition on acetyl-CoA formation was observed when Cd²⁺ was in the medium. After removing metals from sludge, the lipid accumulation was only around half of the one without metal removal. It would be due to that not only the toxic metals in the sludge were removed as well as the metals such as Zn²⁺ which can enhance lipid accumulation.