Characterization of the steam-exploded spent Shiitake mushroom medium and its efficient conversion to ethanol

Textile azo dyes discolouration using spent mushroom substrate: enzymatic degradation and adsorption mechanisms

This study evaluated the adsorption and enzymatic degradation of azo dyes when using SMS. The laccase present in the SMS was characterised, and the maximum activity was obtained at pH 2, a temperature of 45°C, a Michaelis-Menten constant (Km) of 0.264 mM, and a maximum reaction rate (Vmax) of 117.95 µmol L-1 min-1. The presence of NaCl at 5 mM inhibited enzyme activity while no inhibition was observed by Na2SO4, typically found in textile wastewater. The maximum dye adsorption (57.22%) was achieved at pH 8.0, 25°C, and 100 g L-1 of SMS while the maximum enzymatic degradation (14.18%) was obtained under the same conditions, except at pH 4.0. The enzymes laccase, lignin peroxidase, and manganese peroxidase trapped in the SMS resulted in higher dye discolouration when compared to that extracted with aqueous solution, meaning that SMS has strong adsorption capacity and is a natural immobilisation matrix, which improves the enzymatic degradation of the dyes. Thus, SMS can be used in the treatment of textile effluents for dye removal by simultaneous mechanisms of adsorption and enzymatic degradation, with reduction of environmental impacts for SMS disposal and reduction of the costs associated with commercial enzymes and adsorbents.

Extraction and utilization of active substances from edible fungi substrate and residue: A review

The expansion of the edible fungi industry has resulted in the production of large amounts of edible fungus residues, causing great pressure on environmental protection.Therefore, research on edible fungus residue utilization has become a controversial issue. Thus far, numerous efforts have been devoted to separate active substances from edible fungus substrates and residues for high application value utilization. Building upon this, the main methods for extracting active substances from edible mushroom residues are reviewed, and the mechanisms, influencing factors, and trade-offs of the various methods are analysed. Furthermore, the existing and possible directions of utilization of the extracted active substances are reviewed and discussed. Finally, challenges and prospects for the extraction and utilization of different substances in edible fungus residues are proposed. This review provides an effective strategy for protecting the ecological environment and promoting the sustainable development of human society.

Combined Biological and Chemical/Physicochemical Pretreatment Methods of Lignocellulosic Biomass for Bioethanol and Biomethane Energy Production—A Review

Lignocellulosic biomass is a low-cost and environmentally-friendly resource that can be used to produce biofuels such as bioethanol and biogas, which are the leading candidates for the partial substitution of fossil fuels. However, the main challenge of using lignocellulosic materials for biofuel production is the low accessibility to cellulose for hydrolysis of enzymes and microorganisms, which can be overcome by pretreatment. Biological and chemical pretreatments have their own disadvantages, which could be reduced by combining the two methods. In this article, we review biological–chemical combined pretreatment strategies for biogas and bioethanol production. The synergy of fungal/enzyme–NaOH pretreatment is the only biological–chemical combination studied for biogas production and has proven to be effective. The use of enzyme, which is relatively expensive, has the advantage of hydrolysis efficiency compared to fungi. Nonetheless, there is vast scope for research and development of other chemical–biological combinations for biogas production. With respect to ethanol production, fungal–organosolv combination is widely studied and can achieve a maximum of 82% theoretical yield. Order of pretreatment is also important, as fungi may reduce the accessibility of cellulose made available by prior chemical strategies and suppress lignin degradation. The biofuel yield of similarly pretreated biomass can vary depending on the downstream process. Therefore, new strategies, such as bioaugmentation and genetically engineered strains, could help to further intensify biofuel yields.

Poly(ε-L-lysine) and poly(L-diaminopropionic acid) co-produced from spent mushroom substrate fermentation: potential use as food preservatives

Poly(ε-L-lysine) and poly(L-diaminopropionic acid) are valuable homopoly (amino acids) with antimicrobial properties and mainly produced in submerged fermentation. In this study, we investigated their co-production using waste biomass and spent mushroom substrate in solid-state fermentation. Simultaneous production of poly(L-diaminopropionic acid) and poly(ε-L-lysine) was achieved in a single fermentation process using pearl oyster mushroom residues as substrate, with the supplement of glycerol and corn steep liquor. After optimization of the fermentation parameters, the maximum yield of poly(ε-L-lysine) and poly(L-diaminopropionic acid) reached 51.4 mg/g substrate and 25.4 mg/g substrate, respectively. The optimal fermentation conditions were 70% initial moisture content, pH of 6.5, 30°C and an inoculum size of 14%. Furthermore, the fermentation time was reduced from 8 days to 6 days using repeated-batch solid-state fermentation. Finally, the antimicrobial effects of poly(L-diaminopropionic acid) and poly(ε-L-lysine) were evaluated in freshly pressed grape juice, which indicated tremendous potential of this mixture in its use as biological preservative.

Spent mushroom substrates for ethanol production - Effect of chemical and structural factors on enzymatic saccharification and ethanolic fermentation of Lentinula edodes-pretreated hardwood

Spent mushroom substrates (SMS) from cultivation of shiitake (Lentinula edodes) on three hardwood species were investigated regarding their potential for cellulose saccharification and for ethanolic fermentation of the produced hydrolysates. High glucan digestibility was achieved during enzymatic saccharification of the SMSs, which was related to the low mass fractions of lignin and xylan, and it was neither affected by the relative content of lignin guaiacyl units nor the substrate crystallinity. The high nitrogen content in SMS hydrolysates, which was a consequence of the fungal pretreatment, was positive for the fermentation, and it ensured ethanol yields corresponding to 84-87% of the theoretical value in fermentations without nutrient supplementation. Phenolic compounds and acetic acid were detected in the SMS hydrolysates, but due to their low concentrations, the inhibitory effect was limited. The solid leftovers resulting from SMS hydrolysis and the fermentation residues were quantified and characterized for further valorisation.

Ultrasound-assisted extraction of polysaccharide from spent Lentinus edodes substrate: Process optimization, precipitation, structural characterization and antioxidant activity

Lentinus edodes is the second-most popular and cultivated mushroom worldwide due to its nutritional and health-promoting benefit. However, the mushroom production generates vast amounts of spent L. edodes substrate (SLS) that is generally discharged into the environment, posing a great challenge within mushroom by-product valorization. In this work, SLS polysaccharide (SP) was ultrasonically extracted by optimizing the process conditions with response surface methodology. Using gradient ethanol precipitation, SP was separated into SP40, SP60 and SP80, and their monosaccharide composition, structural properties, and antioxidant potential were further characterized and compared. The results showed the total polysaccharide content reached up to 37.05 ± 0.31 mg/g under the optimal conditions including an extraction temperature of 50 °C, a liquid-solid ratio of 30 mL/g and an ultrasonic power of 120 W. SP and its fractional precipitations were heteropolysaccharides sharing a similar monosaccharide composition including L-rhamnose, D-glucuronic acid, D-galacturonic acid, d-glucose and D-xylose, and a typical infrared spectrum for polysaccharide. These fractions also varied in the surface morphology, where SP80 was looser and more porous than SP40 and SP60. Furthermore, SP and SP80 displayed the strongest antioxidant activities in vitro. This study identified a novel and practical strategy to valorize SLS for valuable polysaccharide.

Fiber degradation and carbohydrate production by combined biological and chemical/physicochemical pretreatment methods of lignocellulosic biomass - A review

Sustainable biorefinery concepts based on lignocellulosic biomass are gaining worldwide research interest because of their inexpensiveness and abundance. The recalcitrance of lignocellulosic biomass poses a major hindrance to enhance biofuel production. Therefore, a pretreatment step is critical to prepare the substrates for the downstream process. Combining pretreatment steps help to lower the severity of the drawbacks of a single pretreatment step. This paper systematically reviews the combined biological and chemical/physicochemical pretreatment based on fiber degradation and sugar yield. An energy-efficient biological pretreatment method combined with a chemical pretreatment that accelerates the pretreatment times has been seen to be efficient for fiber degradation and sugar yields. However, fungal species, culture conditions, biomass type, the severity of chemical pretreatment and the order of sequential pretreatment influences the relative component contents and sugar yield. Even the same biomass from different sources undergoing similar pretreatment conditions could result in a varying amount of digestibility.

Proof-of-Concept of Spent Mushrooms Compost Torrefaction—Studying the Process Kinetics and the Influence of Temperature and Duration on the Calorific Value of the Produced Biocoal

Poland, being the 3rd largest and growing producer of mushrooms in the world, generates almost 25% of the total European production. The generation rate of waste mushroom spent compost (MSC) amounts to 5 kg per 1 kg of mushrooms produced. We proposed the MSC treatment via torrefaction for the production of solid fuel—biocoal. In this research, we examined the MSC torrefaction kinetics using thermogravimetric analyses (TGA) and we tested the influence of torrefaction temperature within the range from 200 to 300 °C and treatment time lasting from 20 to 60 min on the resulting biocoal’s (fuel) properties. The estimated value of the torrefaction activation energy of MSC was 22.3 kJ mol−1. The highest calorific value = 17.9 MJ kg−1 d.m. was found for 280 °C (60 min torrefaction time). A significant (p < 0.05) influence of torrefaction temperature on HHV increase within the same group of torrefaction duration, i.e., 20, 40, or 60 min, was observed. The torrefaction duration significantly (p < 0.05) increased the HHV for 220 °C and decreased HHV for 300 °C. The highest mass yield (98.5%) was found for 220 °C (60 min), while the highest energy yield was found for 280 °C (60 min). In addition, estimations of the biocoal recirculation rate to maintain the heat self-sufficiency of MSC torrefaction were made. The net quantity of biocoal (torrefied MSC; 65.3% moisture content) and the 280 °C (60 min) torrefaction variant was used. The initial mass and energy balance showed that MSC torrefaction might be feasible and self-sufficient for heat when ~43.6% of produced biocoal is recirculated to supply the heat for torrefaction. Thus, we have shown a concept for an alternative utilization of abundant biowaste (MSC). This research provides a basis for alternative use of an abundant biowaste and can help charting improved, sustainable mushroom production.

Energy-efficient substrate pasteurisation for combined production of shiitake mushroom (Lentinula edodes) and bioethanol

Hot-air (75-100 °C) pasteurisation (HAP) of birch-wood-based substrate was compared to conventional autoclaving (steam at 121 °C) with regard to shiitake growth and yield, chemical composition of heat-pretreated material and spent mushroom substrate (SMS), enzymatic digestibility of glucan in SMS, and theoretical bioethanol yield. Compared to autoclaving, HAP resulted in faster mycelial growth, earlier fructification, and higher or comparable fruit-body yield. The heat pretreatment methods did not differ regarding the fractions of carbohydrate and lignin in pretreated material and SMS, but HAP typically resulted in lower fractions of extractives. Shiitake cultivation, which reduced the mass fraction of lignin to less than half of the initial without having any major impact on the mass fraction of glucan, enhanced enzymatic hydrolysis of glucan about four-fold. The choice of heating method did not affect enzymatic digestibility. Thus, HAP could substitute autoclaving and facilitate combined shiitake mushroom and bioethanol production.

Anti-inflammatory effect of aqueous extracts of spent Pleurotus ostreatus substrates in mouse ears treated with 12-O-tetradecanoylphorbol-13-acetate

Aims:

To evaluate the application of spent Pleurotus ostreatus substrates, enriched or not with medicinal herbs, as a source of anti-inflammatory compounds.

Subjects and Methods:

P. ostreatus was cultivated on five different substrates: Barley straw (BS) and BS combined 80:20 with medicinal herbs (Chenopodium ambrosioides L. [BS/CA], Rosmarinus officinalis L. [BS/RO], Litsea glaucescens Kunth [BS/LG], and Tagetes lucida Cav. [BS/TL]). The anti-inflammatory activity of aqueous extracts of spent mushroom substrates (SMSs) (4 mg/ear) was studied using an acute inflammation model in the mouse ear induced with 2.5 μg/ear 12-O-tetradecanoylphorbol13-acetate (TPA).

Results:

Groups treated with BS/CA, BS/RO, and BS/LG aqueous extracts exhibited the best anti-inflammatory activity (94.0% ± 5.5%, 92.9% ± 0.6%, and 90.4% ± 5.0% inhibition of auricular edema [IAO], respectively), and these effects were significantly different (P < 0.05) from that of the positive control indomethacin (0.5 mg/ear). BS/TL and BS were also able to reduce TPA-induced inflammation but to a lesser extent (70.0% ± 6.7% and 43.5% ± 6.6% IAO, respectively).

Conclusions:

Spent P. ostreatus substrate of BS possesses a slight anti-inflammatory effect. The addition of CA L. to mushroom substrate showed a slightly synergistic effect while RO L. had an additive effect. In addition, LG Kunth and TL Cav. enhanced the anti-inflammatory effect of SMS. However, to determine whether there is a synergistic or additive effect, it is necessary to determine the anti-inflammatory effect of each medicinal herb.

Conversion of agroindustrial residues for high poly(γ-glutamic acid) production by Bacillus subtilis NX-2 via solid-state fermentation

Poly(γ-glutamic acid) (γ-PGA) production by Bacillus subtilis NX-2 was carried out through solid-state fermentation with dry mushroom residues (DMR) and monosodium glutamate production residues (MGPR; a substitute of glutamate) for the first time. Dry shiitake mushroom residue (DSMR) was found to be the most suitable solid substrate among these DMRs; the optimal DSMR-to-MGPR ratio was optimized as 12:8. To increase γ-PGA production, industrial waste glycerol was added as a carbon source supplement to the solid-state medium. As a result, γ-PGA production increased by 34.8%. The batch fermentation obtained an outcome of 115.6 g kg(-1) γ-PGA and 39.5×10(8) colony forming units g(-1) cells. Furthermore, a satisfactory yield of 107.7 g kg(-1) γ-PGA was achieved by compost experiment on a scale of 50 kg in open air, indicating that economically large-scale γ-PGA production was feasible. Therefore, this study provided a novel method to produce γ-PGA from abundant and low-cost agroindustrial residues.

Steam explosion treatment for ethanol production from branches pruned from pear trees by simultaneous saccharification and fermentation

This study investigated the production of ethanol from unutilized branches pruned from pear trees by steam explosion pretreatment. Steam pressures of 25, 35, and 45 atm were applied for 5 min, followed by enzymatic saccharification of the extracted residues with cellulase (Cellic CTec2). High glucose recoveries, of 93.3, 99.7, and 87.1%, of the total sugar derived from the cellulose were obtained from water- and methanol-extracted residues after steam explosion at 25, 35, and 45 tm, respectively. These values corresponded to 34.9, 34.3, and 27.1 g of glucose per 100 g of dry steam-exploded branches. Simultaneous saccharification and fermentation experiments were done on water-extracted residues and water- and methanol-extracted residues by Kluyveromyces marxianus NBRC 1777. An overall highest theoretical ethanol yield of 76% of the total sugar derived from cellulose was achieved when 100 g/L of water- and methanol-washed residues from 35 atm-exploded pear branches was used as substrate.

Characterization of oxalic acid pretreatment on lignocellulosic biomass using oxalic acid recovered by electrodialysis

The properties of pretreated biomass and hydrolysate obtained by oxalic acid pretreatment using oxalic acid recovered through electrodialysis (ED) were investigated. Most of the oxalic acid was recovered and some of the fermentation inhibitors were removed by ED. For the original hydrolysate, the ethanol production was very low and fermentable sugars were not completely consumed by Pichia stipitis during fermentation. Ethanol yield was less than 0.12 g/g in all stage. For the ED-treated hydrolysate, ethanol production was increased by up to two times in all stages compared to the original hydrolysate. The highest ethanol production was 19.38 g/l after 72 h which correspond to the ethanol yield of 0.33 g/g. Enzymatic conversion of the cellulose to glucose for all the pretreated biomass was in the range of 76.03 and 77.63%. The hydrolysis rate on each pretreated biomass was not significantly changed when oxalic acid recovered by ED was used for pretreatment.

Influence of steam explosion on physicochemical properties and hydrolysis rate of pure cellulose fibers

The aim of this study is to compare the effect of different steam explosion treatments on the physicochemical properties and the hydrolysis rate of a pure bleached cellulose. The results showed that moderate steam explosion treatments (severity factor below 5.2) did not appear to improve the enzymatic hydrolysis rate of the cellulose fibers. However, characterization of the samples showed a modification of the physicochemical properties of the cellulose, resulting in an increase of the water retention values (WRV) coupled to an increase of the overall crystallinity. For higher treatment intensities, an important thermal degradation of the cellulose was highlighted. This thermal degradation caused an important modification of the cellulose composition which leads to a decrease of the hydrolysis rate.