Ethanol induced response in Phanerochaete chrysosporium and its role in the decolorization of triarylmethane dye

Effects of potential inducers to enhance laccase production and evaluating concomitant enzyme immobilisation

This work investigated non-polar solvent hexane and polar solvents methanol and ethanol as inducers besides a well-known inducer, copper, for laccase production with and without mesoporous silica-covered plastic packing under sterilised and unsterilised conditions. The potential of waste-hexane water, which is generated during the mesoporous silica production process, was also investigated as a laccase inducer. During the study, the free and immobilised laccase activity on the packing was measured. The results showed that the highest total laccase activity, approximately 10,000 Units, was obtained under sterilised conditions with 0.5 mM copper concentration. However, no immobilised laccase activity was detected except in the copper and ethanol sets under unsterilised conditions. The maximum immobilised laccase activity of the sets that used waste hexane as an inducer was 1.25 U/mg packing. According to its significant performance, waste hexane can be an alternative inducer under sterilised conditions. Concomitant immobilised packing showed satisfactory laccase activities and could be a promising method to reduce operation costs and improve the cost-efficiency of enzymatic processes in wastewater treatment plants.

Biochemical activity of soil contaminated with BPS, bioaugmented with a mould fungi consortium and a bacteria consortium

This study analysed the scale of bisphenol S (BPS) toxicity to the soil biochemical activity and is part of a wider effort to find solutions to restore the global soil environment balance, including elimination of the effects of ecosystem pollution with BPA, of which BPS is a significant analogue. However, since there has been no research on the effect of BPS on soil health, the objective of the study was pursued based on increasing the levels of soil contamination with the bisphenol 0, 5, 50 and 500 mg BPS kg^-1 DM of soil and by observing the response of seven soil enzymes: dehydrogenases, catalase, urease, acid phosphatase, alkaline phosphatase, arylsulphatase and β-glucosidase to the growing BPS pressure. The potential negative effect of bisphenol S was offset by bioaugmentation with a bacteria consortium-Pseudomonas umsongensis, Bacillus mycoides, Bacillus weihenstephanensis and Bacillus subtilis-and a fungi consortium Mucor circinelloides, Penicillium daleae, Penicillium chrysogenum and Aspergillus niger. BPS was found to be a significant inhibitor of the soil enzymatic activity and, in consequence, its fertility. Dehydrogenases and acid phosphatase proved to be the most susceptible to BPS pressure. Bioaugmentation with a bacteria consortium offset the negative effect of 500 mg BPS kg^-1 DM of soil by inducing an increase in the activity of acid phosphatase and alkaline phosphatase, whereas the fungi consortium stimulated the activity of β-glucosidase and acid phosphatase. A spectacular dimension of bisphenol S inhibition corresponded with both the spring rape above-ground parts and root development disorders and the content of Ca and K in them. The BPS level in soil on day 5 of the experiment decreased by 61% and by another 19% on day 60.

Penicillium purpurogenum cultures under ethanol-induced stress and its correlation with fungal adhesion and biodegrading ability

Fungi are known to be affected by external environmental stimuli, resulting in different stress response effects, which in turn could be used to enhance its biodegrading ability. In a previous study, ethanol was used to manipulate cell-cell and cell-surface interaction to prevent cell loss and maximize the usage of Penicillium purpurogenum cells in the media, a correlation was drawn between ethanol oxidative stress, surface-bound proteins and fungal adhesion. The present study focuses on a more detailed study of the effect of ethanol on the same fungus. The results show that the presence of Yap1p gene and the detection of an oxidized form of glutathione (GSSG) suggest that a stress response might be involved in the adhesion process. The process of adhesion could be described as a signaling process and it is affected by the germ tube formation as an initial step in adhesion. Protein profile showed polymorphism in surface-bound proteins for cultures amended with ethanol when compared to control cultures. Ethanol also affected the DNA polymorphic profile of DNA, rendering the fungus genetically variable. P. purpurogenum produced phenol oxidase enzyme and could be used to degrade total phenols in olive mill waste water without the formation of biofilm on the surface of the containers.

Phylogenetic and metabolic diversity of Tunisian forest wood-degrading fungi: a wealth of novelties and opportunities for biotechnology

In this study, 51 fungal strains were isolated from decaying wood samples collected from forests located in the Northwest of Tunisia in the vicinity of Bousalem, Ain Draham and Kef. Phylogenetic analysis based on the sequences of the internal transcribed spacers of the ribosomal DNA showed a high diversity among the 51 fungal isolates collection. Representatives of 25 genera and 29 species were identified, most of which were members of one of the following phyla (Ascomycota, Basidiomycota and Zygomycota). In addition to the phylogenetic diversity, a high diversity of secreted enzyme profiles was also detected among the fungal isolates. All fungal strains produced at least one of the following enzymes: laccase, cellulase, protease and/or lipase.

Malachite green decolorization by the filamentous fungus Myrothecium roridum--Mechanistic study and process optimization

The filamentous fungus Myrothecium roridum isolated from a dye-contaminated area was investigated in terms of its use for the treatment of Malachite green (MG). The mechanisms involved in this process were established. Peroxidases and cytochrome P-450 do not mediate MG elimination. The laccase of M. roridum IM 6482 was found to be responsible for the decolorization of 8-11% of MG. Thermostable low-molecular-weight factors (LMWF) resistant to sodium azide were found to be largely involved in dye decomposition. In addition, MG decolorization by M. roridum IM 6482 occurred in a non-toxic manner. Data from antimicrobial tests showed that MG toxicity decreased after decolorization. To optimize the MG decolorization process, the effects of operational parameters (such as the medium pH and composition, process temperature and culture agitation) were examined. The results demonstrate that M. roridum IM 6482 may be used effectively as an alternative to traditional decolorization agents.

Ethanol effect on metabolic activity of the ethalogenic fungus Fusarium oxysporum

Background

Fusarium oxysporum is a filamentous fungus which has attracted a lot of scientific interest not only due to its ability to produce a variety of lignocellulolytic enzymes, but also because it is able to ferment both hexoses and pentoses to ethanol. Although this fungus has been studied a lot as a cell factory, regarding applications for the production of bioethanol and other high added value products, no systematic study has been performed concerning its ethanol tolerance levels.

Results

In aerobic conditions it was shown that both the biomass production and the specific growth rate were affected by the presence of ethanol. The maximum allowable ethanol concentration, above which cells could not grow, was predicted to be 72 g/L. Under limited aeration conditions the ethanol-producing capability of the cells was completely inhibited at 50 g/L ethanol. The lignocellulolytic enzymatic activities were affected to a lesser extent by the presence of ethanol, while the ethanol inhibitory effect appears to be more severe at elevated temperatures. Moreover, when the produced ethanol was partially removed from the broth, it led to an increase in fermenting ability of the fungus up to 22.5%. The addition of F. oxysporum’s system was shown to increase the fermentation of pretreated wheat straw by 11%, in co-fermentation with Saccharomyces cerevisiae.

Conclusions

The assessment of ethanol tolerance levels of F. oxysporum on aerobic growth, on lignocellulolytic activities and on fermentative performance confirmed its biotechnological potential for the production of bioethanol. The cellulolytic and xylanolytic enzymes of this fungus could be exploited within the biorefinery concept as their ethanol resistance is similar to that of the commercial enzymes broadly used in large scale fermentations and therefore, may substantially contribute to a rational design of a bioconversion process involving F. oxysporum. The SSCF experiments on liquefied wheat straw rich in hemicellulose indicated that the contribution of the metabolic system of F. oxysporum in a co-fermentation with S. cerevisiae may play a secondary role.