Potential of acid-tolerant microalgae, Desmodesmus sp. MAS1 and Heterochlorella sp. MAS3, in heavy metal removal and biodiesel production at acidic pH.

Highlights • Acid-tolerant microalgae (AM) tolerated heavy metals (HMs) at pH 3.5. • Specific growth rate in AM increased in cultures grown on Mn and Zn. • Cellular analysis revealed the predominant intracellular accumulation of HMs. • Biodiesel production increased in HMs-grown AM at acidic pH. • First report on HMs removal and biodiesel production by AM at pH 3.5. Abstract Metals in traces are vital for microalgae but their occurrence at high concentrations in habitats is a serious ecological concern. We investigated the potential of two acid-tolerant microalgae, Desmodesmus sp. MAS1 and Heterochlorella sp. MAS3, isolated from neutral environments, for simultaneous removal of heavy metals such as copper (Cu), iron (Fe), manganese (Mn) and zinc (Zn), and production of biodiesel when grown at pH 3.5. Excepting Cu, the selected metals at concentrations of 10–20 mg L−1 supported good growth of both the strains. Cellular analysis for metal removal revealed the predominance of intracellular mechanism in both the strains resulting in 40–80 and 40–60% removal of Fe and Mn, respectively. In-situ transesterification of biomass indicated enhanced biodiesel yield with increasing concentrations of metals suggesting that both these acid-tolerant microalgae may be the suitable candidates for simultaneous remediation, and sustainable biomass and biodiesel production in environments like metal-rich acid mine drainages. [ABSTRACT FROM AUTHOR]