Extracellular laccase production and phenolic degradation by an olive mill wastewater isolate

Abstract

Olive mill wastewater (OMWW) presents a challenge to the control of effluents due to the presence of a high organic load, antimicrobial agents (monomeric-polymeric phenols, volatile acids, polyalcohols, and tannins), salinity and acidity. In this study, the production of extracellular laccase, monomeric or polymeric phenol, from an OMWW isolate based on its ability to biodegrade phenols and gallic acid as a model of phenolic compounds in OMWW was investigated. Phylogenetic analysis of the 16S RNA gene sequences identified the bacterial isolate (Acinetobacter REY) as being closest to Acinetobacter pittii. This isolate exhibited a constitutive production of extracellular laccase with an activity of 1.5 and 1.3 U ml/L when supplemented with the inducers CuSO4 and CuSO4+phenols, respectively. Batch experiments containing minimal media supplemented with phenols or gallic acid as the sole carbon and energy source were performed in order to characterize their phenolic biodegradability. Acinetobacter REY was capable of biodegrading up to 200 mg/L of phenols and gallic acid both after 10 h and 72 h, respectively.

Genomic analysis uncovers laccase-coding genes and biosynthetic gene clusters encoding antimicrobial compounds in laccase-producing Acinetobacter baumannii

“…Naturally, bacteria produce low concentrations of laccases, but the synthesis of the enzyme can be increased by adding inducers, such as CuSO 4 3 . However, the optimal Cu concentration for the highest laccase production previously reported ranged from 0.5 to 2 mM 12 , 14 . Enzyme production and bacterial growth were inhibited under higher concentrations of Cu 2+ 14 .…”

“…have attracted attention in environmental and biotechnological applications. Some strains of this genus are known to oxidize aromatic organic pollutants 1 , 2 , 12 . In this study, we isolated 12 strains of Acinetobacter from water and five strains from soil.…”

“…Previous reports of laccase-producing bacteria found that their enzymes can oxidize a broad range of substrates, such as phenol, pyrocatechol, syringaldazine, ABTS and guaiacol 13 . Kumar et al 12 isolated Acinetobacter pittii from olive mill wastewater (OMWW) based on its ability to biodegrade phenols and gallic acid. Using the ABTS substrate supplemented with CuSO 4 , this isolate was found to produce extracellular laccase with 1.5 U/mL activity.…”

“…Genomic information of laccase-producing bacteria is needed for understanding and applying these bacteria in industrial settings. DNA sequencing technologies play important roles in synthetic biology, which include improving microbial strain development for existing and novel bioproduct screening, discovering genes and pathways, and optimizing and understanding metabolic engineering of large-scale manufacturing 12 . Hence, in this study, we aimed to isolate laccase-producing Acinetobacter species, and to identify and perform genomic analysis of the laccase-coding genes and secondary metabolite biosynthesis genes of these isolates.…”