Chromium and Lead Phytoremediation with Water Hyacinth and Use of Contaminated Biomass as Feedstock for Biofuel Production

One of the main drawbacks of the phytoremediation process is the formation of contaminated biomass as secondary pollution. However, this biomass can be utilized as a valuable carbohydrate source with its high sugar content. In this study, the water hyacinth (WH) was used for lead (Pb2+) and chromium (Cr6+) phytoremediation, and the heavy metal contaminated biomass was used as carbohydrate source for biobutanol production. Accumulation of metals was monitored in the root and shoot parts of the plant. Chromium and lead mostly accumulated in the roots with the values of 0.566 mg Cr6+.g(-1) and 12.75 mg Pb2+.g(-1) biomass. Chromium and lead concentrations in the shoot part of WH were measured as 0.093 mg Cr6+.g(-1) and 0.453 mg Pb2+.g(-1). The bioconcentration factor (BCF) was calculated as 56.6 and 1275.2 for chromium and lead, respectively. The contaminated biomass was subjected to dilute acid pretreatment and enzymatic hydrolysis before biobutanol production by Clostridium acetobutylicum DSMZ 1732. Butanol titer of chromium-contaminated biomass was found to be 32% lower than that of lead-contaminated biomass. In the present study, the WH was shown to be a good candidate for lead phytoremediation and it was realized that contaminated biomass has a high potential to be used as feedstock for biofuel production via microbial fermentation.