Use of sawdust for production of ligninolytic enzymes by white-rot fungi and pharmaceutical removal.

Use of white-rot fungi for enzyme-based bioremediation of wastewater is of high interest. These fungi produce considerable amounts of extracellular ligninolytic enzymes during solid-state fermentation on lignocellulosic materials such as straw and sawdust. We used pure sawdust colonized by Pleurotus ostreatus, Trametes versicolor, and Ganoderma lucidum for extraction of ligninolytic enzymes in aqueous suspension. Crude enzyme suspensions of the three fungi, with laccase activity range 12-43 U/L and manganese peroxidase activity range 5-55 U/L, were evaluated for degradation of 11 selected pharmaceuticals spiked at environmentally relevant concentrations. Sulfamethoxazole was removed significantly in all treatments. The crude enzyme suspension from P. ostreatus achieved degradation of wider range of pharmaceuticals when the enzyme activity was increased. Brief homogenization of the colonized sawdust was also observed to be favorable, resulting in significant reductions after a short exposure of 5 min. The highest reduction was observed for sulfamethoxazole which was reduced by 84% compared to an autoclaved control without enzyme activity and for trimethoprim which was reduced by 60%. The compounds metoprolol, lidocaine, and venlafaxine were reduced by approximately 30% compared to the control. Overall, this study confirmed the potential of low-cost lignocellulosic material as a substrate for production of enzymes from white-rot fungi. However, monitoring over time in bioreactors revealed a rapid decrease in enzymatic ligninolytic activity.

Production of oyster mushroom (Pleurotus ostreatus) on sawdust supplemented with anaerobic digestate.

Anaerobic digestion of organic waste results in production of biogas and a nutrient-rich digestate that has an established use as fertilizer in plant production. This study evaluated use of anaerobic digestate based on a high concentration of organic household waste as a fertilizer in sawdust-based production of oyster mushrooms (Pleurotus ostreatus). Inclusion of 0.5 L of anaerobic digestate (AD) per kg sawdust gave similar productivity in terms of biological efficiency (79.5 ± 5.4 %), and protein concentration (24.7 ± 2.4 % of dry weight (dw)) as standard mushroom substrate (78.1 ± 5.3 %, and 21.9 ± 3.0 % of dw, respectively). However, mushroom growth was impaired at the highest concentration of anaerobic digestate tested, 1 L digestate per kg dw sawdust. Comparison of the AD-fertilized substrate with a mushroom substrate with standard components (sawdust, wheat bran, calcium sulfate) and with similar C/N-ratio revealed some differences in elemental composition of the fruiting bodies, with an major increase in sodium concentration for the AD-fertilized substrate compared with the standard substrate (413.3 ± 28.9 and 226.7 ± 30.6 mg kg-1 dw, respectively). This difference can be explained by high sodium concentration in the anaerobic digestate, most likely due to inclusion of food scraps from households and restaurants in the biodigester feedstock. Screening of both substrates for a total of 133 micropollutants revealed that total sum of micropollutants was significantly higher in the AD-fertilized substrate (258 ± 12 ng/g dw substrate) than in the standard substrate (191 ± 35 ng/g dw substrate). Nitrogen losses during preparation of the AD-fertilized substrate were negligible.

Use of lignocellulosic substrate colonized by oyster mushroom (Pleurotus ostreatus) for removal of organic micropollutants from water.

Efficient removal techniques are urgently needed to remove organic micropollutants (OMPs) from wastewater, in order to protect water resources. In this study, laccase activity of mushroom substrate colonized by Pleurotus ostreatus was evaluated as a novel wastewater treatment method for removal of OMPs, including diclofenac, bicalutamide, lamotrigine, and metformin at environmentally relevant concentrations. Laccase activity of the colonized mushroom substrate was found to be highest, 0.8 enzyme activity (U)/g mushroom substrate wet weight, immediately before initiation of fruiting body formation. The selected OMPs were treated for 5 min with suspensions of mushroom substrate with laccase activity of approximately 50 U/L. Removal of all OMPs was significant, with the highest removal for diclofenac of 90% compared with a control with uncolonized mushroom substrate. To our knowledge, direct use of colonized mushroom substrate in removing diclofenac from water has not been reported previously. Removal efficiency of bicalutamide, lamotrigine, and metformin was 43%, 73%, and 59%, respectively. This demonstrates potential for using mushroom substrate colonized by P. ostreatus for removal of OMPs from wastewater.

Fermentation of Cauliflower and White Beans with Lactobacillus plantarum - Impact on Levels of Riboflavin, Folate, Vitamin B12, and Amino Acid Composition.

As diets change in response to ethical, environmental, and health concerns surrounding meat consumption, fermentation has potential to improve the taste and nutritional qualities of plant-based foods. In this study, cauliflower, white beans, and a 50:50 cauliflower-white bean mixture were fermented using different strains of Lactobacillus plantarum. In all treatments containing cauliflower, the pH was reduced to <4 after 18 h, while treatments containing only white beans had an average pH of 4.8 after 18 h. Following fermentation, the riboflavin, folate, and vitamin B12 content of the cauliflower-white bean mixture was measured, and compared against that of an unfermented control. The riboflavin and folate content of the mixture increased significantly after fermentation. Relative to control samples, riboflavin increased by 76-113%, to 91.6 ± 0.6 µg/100 g fresh weight, and folate increased by 32-60%, to 58.8 ± 2.0 µg/100 g fresh weight. For one bacterial strain, L. plantarum 299, a significant 66% increase in vitamin B12 was observed, although the final amount (0.048 ± 0.013 µg/100 g fresh weight) was only a small fraction of recommended daily intake. Measurements of amino acid composition in the mixture revealed small increases in alanine, glycine, histidine, isoleucine, leucine, and valine in the fermented sample compared to the unfermented control.

Fungi-based treatment of real brewery waste streams and its effects on water quality.

Nutrient-rich liquid waste streams generated during the beer brewing were treated by submerged fungal growth. Among five filamentous fungal strains tested, Pleurotus ostreatus and Trichoderma harzianum were selected for treatment of run-off from spent grain and hot trub, respectively. In both waste streams, nitrogen was well removed by fungal treatment, with a maximum reduction of 91.5 ± 0.5% of total nitrogen in run-off from spent grain treated with P. ostreatus and 77.0 ± 3.1% in hot trub treated with T. harzianum. Removal of phosphorus was considerably lower, with maximum removal of total phosphorus of 30.8 ± 11.1% for the P. ostreatus treatment and 16.6 ± 7.8% for the T. harzianum treatment. Considering the high concentration of phosphorus in the waste sources (320-600 mg L-1), additional techniques for its removal are needed. In the P. ostreatus treatment, a total amount of 13.2 ± 2.2 g L-1 dwt of biomass with a protein concentration of 11.6 ± 2.1% was produced.

Fungi-based treatment of brewery wastewater-biomass production and nutrient reduction.

The beer-brewing process produces high amounts of nutrient-rich wastewater, and the increasing number of microbreweries worldwide has created a need for innovative solutions to deal with this waste. In the present study, fungal biomass production and the removal of organic carbon, phosphorus and nitrogen from synthetic brewery wastewater were studied. Different filamentous fungi with a record of safe use were screened for growth, and Trametes versicolor, Pleurotus ostreatus and Trichoderma harzianum were selected for further work. The highest biomass production, 1.78 ± 0.31 g L-1 of dry weight, was observed when P. ostreatus was used for the treatment, while T. harzianum demonstrated the best capability for removing nutrients. The maximum reduction of chemical oxygen demand, 89% of the initial value, was observed with this species. In the removal of total nitrogen and phosphorus, no significant difference was observed between the species, while removal of ammonium varied between the strains. The maximum reduction of ammonium, 66.1% of the initial value, was also found in the T. harzianum treatment. It can be concluded that all treatments provided significant reductions in all water-quality parameters after 3 days of growth and that the utilisation of filamentous fungi to treat brewery wastewater, linked to a deliberate strategy to use the biomass produced, has future potential in a bio-based society.

Rhizobacterial glutathione levels as affected by starvation and cadmium exposure.

The rhizosphere is a continuously fluctuating environment in which severe stresses are put on its inhabitants, and glutathione, a reducing tripeptide, and related compounds probably have important roles in cellular protection. In the present study the metabolism of glutathione was examined in rhizobacteria subjected to stress. The plant-growth-promoting rhizobacterium Pseudomonas fluorescens 5.014 and its mutant 5-2/4 were exposed to starvation, either by resuspension or exhaustion, and to cadmium. Glutathione levels, cell protein, and viable count were determined and compared in different conditions. Both starvation and cadmium exposure decreased the amount of glutathione in the cell. No changes of the glutathione concentration in the medium were observed with or without the presence of rhizobacteria, indicating that there was no transport over the cell membrane. The glutathione levels within the rhizobacteria may give valuable information on how different stresses affect the bacteria. In this study, the involvement of glutathione in the increased stress resistance earlier observed in nutrient-starved P. fluorescens was not supported. The concentration of bacterial glutathione is suggested as a possible marker for rhizosphere competence, which, however, needs to be further evaluated with several strains of rhizobacteria.