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Laccase–cellobiose dehydrogenase-catalyzed detoxification of phenolic-rich olive processing residues
Nugroho Prasetyo, E.; Rodríguez, R.D.; Lukesch, B.; Weiss, S.; Murkovic, M.; Katsoyannos, E.; Sygmund, C.; Ludwig, R.; Nyanhongo, G.S. & Guebitz, G.M.
Abstract
The combination of a laccase–hydroxybenzotriazole
(HBT) mediator system with/without cellobiose
dehydrogenase (CDH) or an additional Fenton reaction step
for the elimination and/or detoxification of phenolic compounds
in dry olive mill residues (DOR) and liquid olive
mill wastewaters (OMW) was evaluated. The laccase–
HBT–CDH and laccase–HBT–CDH–Fenton system were
the most effective, removing at least 69 and 72 % of
phenolic compounds from a total of 698 and 683 mg in
OMW and DOR, respectively, in 12 h. The efficient
removal of phenolic compounds was also accompanied by
>80 % reduction in biochemical oxygen demand and
chemical oxygen demand in both DOR and OMW.
Microbial community analysis using single-strand conformation
polymorphism (SSCP) gels showed that biogas
reactors supplemented with untreated and laccase–HBT–
CDH–Fenton-treated DOR and OMW strongly inhibited
growth of microorganisms. In contrast, the laccase–HBTand
laccase–HBT–CDH-pretreated OMW and DOR were
detoxified as evidenced by SSCP analysis, which also
indicated a distinct sensitivity of the individual members of
the anaerobic population toward the toxicants. Further,
although the laccase–HBT–CDH–Fenton system was
effective in bleaching and removing phenolic compounds
in both OMW and DOR, it was not able to support methane
production. However, laccase–HBT and laccase–HBT–
CDH indeed supported biogas production. This study
therefore shows that the laccase–HBT–CDH system has a
potential for the detoxification of olive mill residues, which
can be potentially used as substrates for downstream
processes.
Keywords
Olive oil phenolic-rich waste; Laccase; Cellobiose dehydrogenase; Fenton’s reaction; Detoxification; Single-strand conformation polymorphism; Microbial community analysis
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