Consolidated bioprocessing of biomass and synthetic cadmium wastewater substrates for enhancing hydrogen production by Clostridium thermocellum-CdS complex

Abstract

Bioconversion of biomass to bioenergy and recycle of cadmium wastewater are widespread and of significant economic importance. The development of an efficient and cost effective bioconversion process remains challenging. Here, recycling cadmium and un-pretreated biomass conversion were combined into a single operation. A modified consolidated bioprocessing (CBP) strategy of biomass and synthetic cadmium wastewater as mixed substrates for hydrogen generation through a couple of whole-cell catalysis with photocatalysis was established by Clostridium thermocellum. The process was accomplished by biotransformation of cadmium ions to cadmium sulfide (CdS) by C. thermocellum. The formed hybrid C. thermocellum-CdS complex converted biomass into hydrogen production through the integration of two reactions together, biocatalysis and photocatalysis. After optimization, the hydrogen production produced by C. thermocellum-CdS was remarkably increased by 36.1% if compared with that by C. thermocellum only. This exploration is expected to provide a novel strategy of collaborative disposal of cadmium wastewater and waste biomass, which would not only bring a great potential in the recycling and reusing of cadmium wastewater and waste biomass, but also provide new approach both for bioenergy recovery and environmental improvement.