Degradation of Synthetic Dyes by Laccases – A Mini-Review

Laccases provide a promising future as a tool to be used in the field of biodegradation of synthetic dyes with different chemical structures. These enzymes are able to oxidize a wide range of phenolic substrates without the presence of additional co-factors. Laccases have been confirmed for their potential of synthetic dye degradation from wastewater and degradation products of these enzymatic reactions become less toxic than selected dyes. This study discusses the potential of laccase enzymes as agents for laccase-catalyzed degradation in terms of biodegradation efficiency of synthetic dyes, specifically: azo dyes, triphenylmethane, indigo and anthraquinone dyes. Review also summarizes the laccase-catalyzed degradation mechanisms of the selected synthetic dyes, as well as the degradation products and the toxicity of the dyes and their degradation products

Optimization of Propagation Medium for Enhanced Polyhydroxyalkanoate Production by Pseudomonas oleovorans

Polyhydroxyalkanoates (PHAs) represent a promising alternative to commercially used petroleum-based plastics. Pseudomonas oleovorans is a natural producer of medium-chain-length PHA (mcl-PHA) under cultivation conditions with nitrogen limitation and carbon excess. Two-step cultivation appears to be an efficient but more expensive method of PHA production. Therefore, the aim of this work was to prepare a minimal synthetic medium for maximum biomass yield and to optimize selected independent variables by response surface methodology (RSM). The highest biomass yield (1.71 ± 0.04 g/L) was achieved in the optimized medium containing 8.4 g/L glucose, 5.7 g/L sodium ammonium phosphate and 35.4 mM phosphate buffer. Under these conditions, both carbon and nitrogen sources were completely consumed after 48 h of the cultivation and the biomass yield was 1.7-fold higher than in the conventional medium recommended by the literature. This approach demonstrates the possibility of using two-stage PHA cultivation to obtain the maximum amount of biomass and PHA

Optimization of Propagation Medium for Enhanced Polyhydroxyalkanoate Production by <i>Pseudomonas oleovorans</i>

Polyhydroxyalkanoates (PHAs) represent a promising alternative to commercially used petroleum-based plastics. Pseudomonas oleovorans is a natural producer of medium-chain-length PHA (mcl-PHA) under cultivation conditions with nitrogen limitation and carbon excess. Two-step cultivation appears to be an efficient but more expensive method of PHA production. Therefore, the aim of this work was to prepare a minimal synthetic medium for maximum biomass yield and to optimize selected independent variables by response surface methodology (RSM). The highest biomass yield (1.71 ± 0.04 g/L) was achieved in the optimized medium containing 8.4 g/L glucose, 5.7 g/L sodium ammonium phosphate and 35.4 mM phosphate buffer. Under these conditions, both carbon and nitrogen sources were completely consumed after 48 h of the cultivation and the biomass yield was 1.7-fold higher than in the conventional medium recommended by the literature. This approach demonstrates the possibility of using two-stage PHA cultivation to obtain the maximum amount of biomass and PHA

Optimization of Growth Conditions to Enhance PHA Production by <i>Cupriavidus necator</i>

The accumulation of polyhydroxyalkanoates (PHAs) by microorganisms usually occurs in response to environmental stress conditions. Therefore, it is advantageous to choose two-step cultivation. The first phase is aimed at maximizing biomass production, and only in the second phase, after setting the suitable conditions, PHA production starts. The aim of this work was to optimize the composition of the minimal propagation medium used for biomass production of Cupriavidus necator DSM 545 using the response surface methodology (RSM). Based on the results from the search for optimization limits, the glucose concentration, the ammonium sulfate concentration and the phosphate buffer molarity were chosen as independent variables. The optimal values were found as follows: the glucose concentration 10.8 g/L; the ammonium sulfate concentration 0.95 g/L; and the phosphate buffer molarity 60.2 mmol/L. The predicted biomass concentration was 4.54 g/L, and the verified value was at 4.84 g/L. Although this work was primarily focused on determining the optimal composition of the propagation medium, we also evaluated the optimal composition of the production medium and found that the optimal glucose concentration was 6.7 g/L; the ammonium sulfate concentration 0.60 g/L; and the phosphate buffer molarity 20 mmol/L. The predicted PHB yield was 54.7% (w/w) of dry biomass, and the verified value was 49.1%