Fungal Bioremediation of the ß-Lactam Antibiotic Ampicillin under Laccase-Induced Conditions.

Due to widespread overuse, pharmaceutical compounds, such as antibiotics, are becoming increasingly prevalent in greater concentrations in aquatic ecosystems. In this study, we investigated the capacity of the white-rot fungus, Coriolopsis gallica (a high-laccase-producing fungus), to biodegrade ampicillin under different cultivation conditions. The biodegradation of the antibiotic was confirmed using high-performance liquid chromatography, and its antibacterial activity was evaluated using the bacterial growth inhibition agar well diffusion method, with Escherichia coli as an ampicillin-sensitive test strain. C. gallica successfully eliminated ampicillin (50 mg L-1) after 6 days of incubation in a liquid medium. The best results were achieved with a 9-day-old fungal culture, which treated a high concentration (500 mg L-1) of ampicillin within 3 days. This higher antibiotic removal rate was concomitant with the maximum laccase production in the culture supernatant. Meanwhile, four consecutive doses of 500 mg L-1 of ampicillin were removed by the same fungal culture within 24 days. After that, the fungus failed to remove the antibiotic. The measurement of the ligninolytic enzyme activity showed that C. gallica laccase might participate in the bioremediation of ampicillin.

Optimized decolorization of two poly azo dyes Sirius Red and Sirius Blue using laccase-mediator system.

Factors, namely pH, laccase-like activity, dyes concentration as well as 1-Hydroxybenzotriazole (HBT) concentration was examined. The results indicated that the maximum decolorization yield and rate reached 98.30 ± 0.10% and 5.84 ± 0.01%/min, respectively for Sirius Blue, and 99.34 ± 0.47% and 5.85 ± 0.12%/min, respectively for Sirius Red after 4 h. The presence of the redox mediator 1-hydroxybenzotriazole (HBT) greatly improved the decolorization levels. The optimum concentrations of HBT, dyes, and laccase were 0.62 mM, 50 mg/L, and 0.89 U/mL respectively at pH 4.58 for both dyes. Phytotoxicity tests using treated and untreated dyes proved that the applied treatment slightly decreased the toxicity of the by-products. However, the germination index (GI) increased from 14.6 to 36.08% and from 31.6 to 36.96% for Sirius Red and Sirius Blue, respectively. The present study focused on the treatment of two recalcitrant azo dyes, namely: Sirius Blue (Direct Blue 71) and Sirius Red (Direct Red 80). The decolorization was performed using cell-free supernatant from Coriolopsis gallica culture with high laccase activity. Response surface methodology (RSM) and Box-Behnken design were applied to optimize the decolorization of the two tested dyes. The effect of four.

Optimization of reactive black 5 decolorization by the newly isolated Saccharomyces cerevisiae X19G2 using response-surface methodology.

In the current investigation, the capacity of different yeast strains to decolorize reactive black 5 (RB-5) was assessed. A comparative study between the different strains demonstrated that Saccharomyces cerevisiae X19G2 exhibited the highest decolorization rate (69.20 ± 1.16%) after 48 h of incubation. This strain was selected to optimize the medium components' concentrations for maximum RB-5 decolorization. Response-surface methodology (RSM) was tested for the most significant parameters (glucose, yeast extract and RB-5 dye concentrations) that were previously determined by Plackett-Burman design. A dye decolorization rate of 99.59 ± 0.24% was achieved within 48 h using a maximum RB-5 concentration (0.15 g/L) with glucose and yeast extract concentrations equalling to 10.5 g/L and 1 g/L, respectively. Experimental data results proved to fit well with the pseudo-second order kinetics model. The phytotoxicity assessment was carried out using Raphanus sativus seeds to determine the toxicity of RB-5 before and after treatment by S. cerevisiae. Results suggested that germination rate and the length of seeds radical irrigated with 0.15 g/L of RB-5 decreased by 30 and 53%, compared to those irrigated with treated solution. Therefore, metabolites derived from decolorization of RB-5 by S. cerevisiae X19G2 were significantly less toxic than the original dye.

A Comparative Study of Various Pretreatment Approaches for Bio-Ethanol Production from Willow Sawdust, Using Co-Cultures and Mono-Cultures of Different Yeast Strains.

The effect of different pretreatment approaches based on alkali (NaOH)/hydrogen peroxide (H2O2) on willow sawdust (WS) biomass, in terms of delignification efficiency, structural changes of lignocellulose and subsequent fermentation toward ethanol, was investigated. Bioethanol production was carried out using the conventional yeast Saccharomyces cerevisiae, as well as three non-conventional yeasts strains, i.e., Pichia stipitis, Pachysolen tannophilus, Wickerhamomyces anomalus X19, separately and in co-cultures. The experimental results showed that a two-stage pretreatment approach (NaOH (0.5% w/v) for 24 h and H2O2 (0.5% v/v) for 24 h) led to higher delignification (38.3 ± 0.1%) and saccharification efficiency (31.7 ± 0.3%) and higher ethanol concentration and yield. Monocultures of S. cerevisiae or W. anomalus X19 and co-cultures with P. stipitis exhibited ethanol yields in the range of 11.67 ± 0.21 to 13.81 ± 0.20 g/100 g total solids (TS). When WS was subjected to H2O2 (0.5% v/v) alone for 24 h, the lowest ethanol yields were observed for all yeast strains, due to the minor impact of this treatment on the main chemical and structural WS characteristics. In order to decide which is the best pretreatment approach, a detailed techno-economical assessment is needed, which will take into account the ethanol yields and the minimum processing cost.

On the evaluation of different saccharification schemes for enhanced bioethanol production from potato peels waste via a newly isolated yeast strain of Wickerhamomyces anomalus.

The present study focuses on the exploration of the potential use of potato peels waste (PPW) as feedstock for bioethanol production, using a newly isolated yeast strain, Wickerhamomyces anomalus, via different saccharification and fermentation schemes. The saccharification of PPW was performed via thermal and chemical (acid, alkali) pretreatment, as well as via enzymatic hydrolysis through the use of commercial enzymes (cellulase and amylase) or enzymes produced at lab scale (alpha-amylase from Bacillus sp. Gb67), either separately or in mixtures. The results indicated that the enzymatic treatment by commercial enzymes led to a higher saccharification efficiency (72.38%) and ethanol yield (0.49 g/gconsumed sugars) corresponding to 96% of the maximum theoretical. In addition, acid pretreatment was found to be beneficial for the process, leading also to high hydrolysis and ethanol yields, indicating that PPW is a very promising feedstock for bio-ethanol production by W. anomalus under different process schemes.