Biological methods for detoxification of corn stover and corn starch pyrolysis liquors
Biological methods were developed to detoxify corn stover and corn starch pyrolysis liquors produced at 400--500°C. Prokaryotic and eukaryotic suspended cells and biofilms were employed for the detoxification process. The continuous of detoxification process was monitored by measuring the change in dissolved oxygen and pH. Total phenolic assay, change in UV absorbance spectra, GC-MS analysis and bioassay were performed to determine the detoxification. Pseudomonas putida and Streptomyces setonii biofilms, developed on Plastic Composite Supports (PCS) fixed to agitator shaft of benchtop computer controlled bioreactor, detoxified 10 and 25% (v/v) diluted corn stover and corn starch pyrolysis liquor (Des and Dst), while mixed culture biofilms detoxified 50% (v/v) Dcs and Dst.;Ligninolytic enzymes of Phanerochaete chrysosporium were also employed to detoxify the Dcs and Dst in shake flask cultures. The detoxification was determined by measuring the activity of lignin peroxidase (LiP), mangenase peroxidase (MnP), total phenolic compounds reduction, GC-MS analysis, and bioassay. Ph. chrysosporium culture detoxified 10 and 25% (v/v) Dcs and Dst, but not 50% (v/v) Des and Dst. The involvement of ligninolytic enzymes in the detoxification process were confirmed by adding ligninolytic enzymes inhibitors, sodium azide and cycloheximide to culture medium and by employing concentrated crude enzyme to detoxify 10% (v/v) Dcs.;In a subsequent study, the ligninolytic enzymes were produced by Ph. chrysosporium PCS biofilm in stirred tank bioreactor. Fourteen repeated batch fermentations were performed with different culture conditions. The differences in enzymes production between the batches were determined statistically by comparing the activity of LiP and MnP. All batch conditions evaluated enhanced the production of at least one of the enzymes. In batch C3V0 11 and C3V3 8 (continuous aeration, 300 agitation, and addition of veratryl alcohol on day zero or three) LiP and MnP were produced on day three and reached a peak on day six. However, in batch C3VM0 14 (continuous aeration, 300 agitation, and addition of veratryl alcohol and MnSO4 on day zero) LiP and MnP were produced earlier, on day three, and decreased by day six.