Effects of encapsulation on the chemical inhibition of anaerobic hydrogen- and methane-producing microbial cells

Encapsulating microbial cells in an alginate matrix enables high-rate anaerobic biological treatment and resource recovery by increasing cell concentration and retention time. To determine whether encapsulation protected microbial cells from inhibitors, copper(II), chromium(VI) (as dichromate), ammonium, and chloroform were amended to hydrogen-producing anaerobic microbial cells that were either suspended or encapsulated in a composite-coated alginate matrix. Encapsulation mitigated dichromate inhibition by 36% based on the dose-response curve slope but increased ammonium inhibition by 210% and had no effect on inhibition by chloroform. This was explained by effective concentrations in the beads after measuring partition coefficients. Encapsulation rendered copper(II) unavailable through apparent chelation because it protected both the hydrogen-producing and a methane-producing community from copper(II) despite its high effective concentration in encapsulation. Understanding the effects that the encapsulation of microbial cells has on chemical inhibition can help expand the application conditions of wastewater treatment or resource recovery and avoid unanticipated toxicity.