Methane production and characteristics of the microbial community in the co-digestion of spent mushroom substrate with dairy manure

A novel approach to assessing the bioavailability of biopeptide inhibitor of HMG CoA reductase from germinated and ungerminated Kara Kratok (Phaseolus lunatus L.)

Background

The bioavailability of biopeptide compounds is a development challenge, mainly because of their resistance to the digestion system. This study aimed to determine the bioavailability of HMG CoA reductase biopeptide inhibitors from germinated and ungerminated Kara Kratok (Phaseolus lunatus L.).

Methods

Germinated and ungerminated brown P. lunatus were simulated for digestion enzyme in vitro (120 minutes for pepsin and pancreatin), followed by an in situ method for absorption. Perfusate samples were measured for the absorption percentage, inhibition of HMG CoA reductase, molecular weight (MW), peptide concentration, and hydrolysis degree (%DH).

Results

The results showed that germinated brown P. lunatus exhibited the highest absorption (32.42%), and the percentage of HMG CoA reductase inhibition during enzymatic digestion was at 210 minutes (87.51%), with MW < 10 kDa, peptide concentration of 2.39 mg/mL, and %DH of 48.90%. These findings suggest that germinated brown P. lunatus is a potent HMG CoA reductase inhibitor with significantly higher bioavailability than that of its ungerminated counterpart. This finding underscores its superiority in this context and open new possibilities for biopeptide research.

Spent mushroom substrate: A review on present and future of green applications

The cultivation of edible mushrooms plays a significant role in revitalizing numerous rural regions in China. However, this process generates a large amount of spent mushroom substrate (SMS). Traditional methods for handling SMS, such as random stacking and incineration, lead to resource waste and environmental pollution. The content of organic matter in SMS can range from 40% to 60%, and it also contains various beneficial elements such as trace minerals, making it a valuable resource for biomass. This review initially explores the unique characteristics of SMS and then summarizes the main methods of utilizing its resources. Presently, common resource utilization techniques for SMS include using it as a second-generation cultivation substrate, preparing animal feed and soil fertilizer, producing methane, bioethanol, hydrogen, bio-oil, and electrodes of energy storage devices, extracting enzymes and polysaccharides, and creating bioremediation materials for heavy metals and organic pollutants removal. While research has been conducted on these utilization methods, there are still relatively few large-scale industrial applications. This review also highlights existing challenges and potential solutions in the SMS utilization. Upcycling SMS via innovative and practical technologies presents a promising approach to transforming organic waste into economic value.

The inoculation of Bacillus paralicheniformis and Streptomyces thermoviolaceus enhances the lignocellulose degradation and microbial communities during spent mushroom substrate composting

The burgeoning global mushroom industry has precipitated challenges related to the efficient and sustainable utilization of spent mushroom substrate (SMS). Composting is regarded as an efficient way for the ecological utilization of SMS. The addition of microbial inoculants can promote the composting process and improve the quality of compost products. This study introduced two bacterial inoculants, Bacillus paralicheniformis HL-05 (BP) and Streptomyces thermoviolaceus LC-10 (ST), into the composting process of SMS. The impact of these inoculants was evaluated through analyses of physicochemical properties, lignocellulose degradation, and high-throughput sequencing to elucidate their ecological roles and optimize the composting process. The results suggest that inoculation with BP and ST significantly prolonged the thermophilic stage by 2-3 days, representing an increase of 22.22-33.33%. Moreover, it boosted the degradation rates of cellulose, hemicellulose, and lignin by 18.37-29.77%, 35.74-50.43%, and 40.32-40.83%, respectively, compared to the control. Furthermore, inoculation rapidly altered the microbial community structure during the rapid temperature-rising stage and strengthened interconnections among composting microorganisms. The microbial inoculation substantially enhanced the proliferation of thermophilic lignocellulose-degrading microorganisms during the thermophilic stage, thereby facilitating the utilization of lignocellulose. This study proposes a novel and effective strategy for SMS composting using microbial inoculants.

Replacing traditional nursery soil with spent mushroom substrate improves rice seedling quality and soil substrate properties

Currently, large quantities of spent mushroom substrate (SMS) are produced annually. Because SMS has high water retention and nutrients, it has great potential to replace traditional topsoil for raising seedlings in agricultural production. However, few studies have examined the effects of substituting SMS for paddy soil on rice seedling growth and soil nutrients. SMS was mixed with rice soil in different proportions (20%, 50%, and 80%), and chemical fertilizer, organic fertilizer, and peat substrate were added in addition to equivalent nitrogen as a traditional seedling nursery method for comparison. Compared to traditional paddy soil (CK), the seedling qualities of the three SMS ratio treatments were all higher. Adding SMS at different ratios promoted rice seedling root growth, elevated the soluble protein concentration, and amplified the superoxide dismutase (SOD) enzymatic action in rice seedlings. Total porosity and aeration porosity of the soil increased by 17.40% and 32.90%, respectively. Soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) increased by 21.26-118.48%, 50.44-71.68%, and 23.08-80.17%, respectively. Besides, the relative abundance of Bacillus, Bacteroidetes, and other bacteria as well as the abundance of Ascomycota were all significantly increased. Adding 50% SMS increased the abundance of Pseudomonas by 8.42 times. The seedling quality of the 50% SMS treatment was even higher than chemical fertilizer and organic fertilizer treatments, only second to the peat substrate treatment. In summary, partial substitution of paddy soil with SMS can ameliorate substrate properties, improve seedling quality, and increase microbial diversity, indicating the suitability of SMS as a replacement for rice soil in seedling substrates. The 50% SMS ratio is the best. This study provides a basis for SMS to replace traditional rice soil in seedling cultivation.

Optimization of semi-continuous dry anaerobic digestion process and biogas yield of dry yellow corn straw: Based on "gradient anaerobic digestion reactor"

In China, the problem of low biogas yield of traditional biogas projects has become increasingly prominent. This study investigated the effects of different hydraulic retention times (HRTs) on the biogas production efficiency and microbial community under pilot conditions. The results show that the "Gradient anaerobic digestion reactor" can stably carry out semi-continuous dry anaerobic digestion and improve biogas yield. The highest volatile solids (VS) biogas yield (413.73 L/kg VS and 221.61 L CH4/kg VS) and VS degradation rate (48.41%) were observed at an HRT of 25 days. When the HRT was 15 days, the volumetric biogas yield was the highest (2.73 L/L/d, 1.43 L CH4/L/d), but the VS biogas yield and degradation rate were significantly decreased. Microbial analysis showed that HRT significantly affected microbial community. It provides basic data support for the development of a new anaerobic digestion process and the practical application of the straw biogas project in China.

Effect of temperature and storage methods on liquid digestate: Focusing on the stability, phytotoxicity, and microbial community

Identifying the stability and phytotoxicity of liquid digestate (LD) is necessary for safe agricultural utilization. Storage temperature, method, and time are critical factors that affect the stability and phytotoxicity of LD. This study therefore aimed to explore the dynamics of stability, phytotoxicity, and microbial community of LD in cattle farms under different storage conditions. The results showed that the contents of solids, organic matter, nitrogen, and phosphorous decreased during storage and exhibited temperature dependency. Conversely, the seed germination index increased, which was negatively correlated with dissolved organic carbon and ammonium nitrogen and positively correlated with certain bacteria (Thermovirga and Fastidiosipila). Open storage and/or higher temperature were found to contribute to the stabilization efficiency and phytotoxicity disappearance of LD. Open storage of LD at 30 °C for 60 days and 20 °C for 90 days was safe for its agricultural utilization, while hermetic storage of LD at 30 °C for 120 days and 20 °C for 150 days was safe. However, for storage at 10 °C for 180 days, additional post-treatment is required.

Spent Mushroom Substrate Hydrolysis and Utilization as Potential Alternative Feedstock for Anaerobic Co-Digestion

Valorization of lignocellulosic biomass, such as Spent Mushroom Substrate (SMS), as an alternative substrate for biogas production could meet the increasing demand for energy. In view of this, the present study aimed at the biotechnological valorization of SMS for biogas production. In the first part of the study, two SMS chemical pretreatment processes were investigated and subsequently combined with thermal treatment of the mentioned waste streams. The acidic chemical hydrolysate derived from the hydrothermal treatment, which yielded in the highest concentration of free sugars (≈36 g/100 g dry SMS, hydrolysis yield ≈75% w/w of holocellulose), was used as a potential feedstock for biomethane production in a laboratory bench-scale improvised digester, and 52 L biogas/kg of volatile solids (VS) containing 65% methane were produced in a 15-day trial of anaerobic digestion. As regards the alkaline hydrolysate, it was like a pulp due to the lignocellulosic matrix disruption, without releasing additional sugars, and the biogas production was delayed for several days. The biogas yield value was 37 L/kg VS, and the methane content was 62%. Based on these results, it can be concluded that SMS can be valorized as an alternative medium employed for anaerobic digestion when pretreated with both chemical and hydrothermal hydrolysis.

Organic Fertilizers Shape Soil Microbial Communities and Increase Soil Amino Acid Metabolites Content in a Blueberry Orchard

The decline in soil nutrients is becoming a major concern of soil degradation. The possibility of using organic waste as a soil additive to increase nutrients and essential components is significant in soil quality protection and waste management. The aim of this study was to investigate the effects of composted spent mushroom substrate (MS), giant panda feces (PF), and cattle manure (CM) as organic fertilizers in soil microbial communities and metabolites in blueberry orchard in China, which were measured by using high-throughput sequencing and gas chromatography-mass spectrometry (GC-MS)-based metabolomics. Altogether, 45.66% of the bacterial operational taxonomic units (OTUs) and 9.08% of the fungal OTUs were detected in all treatments. Principal coordinates analysis demonstrated that the bacterial and fungal communities in MS and PF treatments were similar, whereas the communities in the not-organic fertilized control (CK) were significantly different from those in the organic fertilizer treatments. Proteobacteria, Acidobacteria, and Bacteroidetes were the dominant bacterial phyla, and Basidiomycota, Ascomycota, and Mortierellomycota the dominant fungal phyla. Redundancy analysis indicated that pH and available potassium were the main factors determining the composition of microbial communities. The fungal genera Postia, Cephalotrichum, and Thermomyces increased in organic fertilizer treatments, and likely promoted the degradation of organic fertilizers into low molecular-weight metabolites (e.g., amino acids). PCA and PLS-DA models showed that the metabolites in CK were different from those in the other three treatments, and those in CM were clearly different from those in MS and PF. Co-occurrence network analysis showed that several taxa correlated positively with amino acid contents. The results of this study provide new insights into organic waste reutilization and new directions for further studies.

Valorization of spent mushroom substrate for low-carbon biofuel production: Recent advances and developments

Due to the nutritional values and functional bioactivities of mushrooms, the global market value of the edible mushroom industry has been growing steadily. However, the production of 1 kg of fresh mushroom generates about 5 kg of wet byproducts (known as spent mushroom substrate; SMS). This necessitates proper waste management to mitigate potential environmental threats. Embracing the "waste-to-fuel" concept, SMS as lignocellulosic waste can serve as cheap and abundant feedstock for the production of a variety of biofuels, including biogas, biohydrogen, bioethanol, bio-oil, and solid-biofuels. Mushroom cultivation serves as efficient biological pretreatment for biofuel production, promoting biofuel yield and improving the overall economy. Therefore, integrated mushroom cultivation and biofuel production can simultaneously satisfy the rapidly rising food and energy demand. The article systematically reviewed the recycling and re-utilization of SMS in sustainable biofuel production, discussing the possible challenges and proposing future directions for the green development of the mushroom industry.

Recent advances in conductive materials amended anaerobic co-digestion of food waste and municipal organic solid waste: Roles, mechanisms, and potential application

Recently, conductive materials (i.e., carbon-based and iron-based materials) as a feasible and attractive approach have been introduced to anaerobic co-digestion (ACoD) system for promoting its performance and stability through direct interspecies electron transfer. Owing to the key roles of conductive materials in ACoD process, it is imperative to gain a profound understanding of their specific functions and mechanisms. Here, this review critically examined the state of the art of conductive materials assisted ACoD of food waste and common municipal organic solid waste. Then, the fundamental roles of conductive materials on ACoD enhancement and the relevant mechanisms were discussed. Last, the perspectives for co-digestate treatment, reutilization, and disposal were summarized. Moreover, the main challenges to conductive materials amended ACoD in on-site application were proposed and the future remarks were put forward. Collectively, this review poses a scientific basis for the potential application of conductive materials in ACoD process in the future.

Analysis of the Composition of Substrate for Industrial Fermentation of Agaricus bisporus Based on Secondary and Tertiary Fermentation Mode Composition Analysis of Industrial Fermentation Substrates of A. bisporus

In this study, changes in metabolites during the fermentation of Agaricus bisporus compost under the Shanghai Lianzhong secondary fermentation method and Jiangsu Yuguan tertiary fermentation method were analysed by applying gas chromatography–mass spectrometry (GC–MS) to understand the differences in metabolites under different fermentation methods and find metabolic markers at different fermentation stages in different fermentation methods. The results showed that 1002 compounds were identified. Based on the differential metabolites from pathways of significant enrichment, it was found that L-aspartic acid and 5-aminobenzolevulinic acid could be used as potential metabolic markers to evaluate the phase 2 fermentation method of Shanghai Lianzhong and the phase 3 fermentation method of Jiangsu Yuguan, respectively. This study provides a reference for the preparation of quality-stable fermentation materials and further understanding of the cultivation of A. bisporus with fermentation materials.

Microbial Activity during Composting and Plant Growth Impact: A Review

Replacing harmful chemical pesticides with compost extracts is steadily gaining attention, offering an effective way for plant growth enhancement and disease management. Food waste has been a major issue globally due to its negative effects on the environment and human health. The methane and other harmful organisms released from the untreated waste have been identified as causes of this issue. Soil bacteria impart a very important role in biogeochemical cycles. The interactions between plants and bacteria in the rhizosphere are some of the factors that determine the health and fertility of the soil. Free-living soil bacteria are known to promote plant growth through colonizing the plant root. PGPR (Plant Growth Promoting Rhizobacteria) inoculants in compost are being commercialized as they help in the improvement of crop growth yield and provide safeguard and resistance to crops from disease. Our focus is to understand the mechanism of this natural, wet waste recycling process and implementation of a sustainable operative adaptation with microbial association to ameliorate the waste recycling system.

Exploring Farm Anaerobic Digester Economic Viability in a Time of Policy Change in the UK

The combination of a post-Brexit agricultural policy, the Global Methane Pledge announced during the last United Nations Climate Change Conference in Glasgow (COP26), and urgency of meeting climate goals means the UK has a unique opportunity to create an exemplar through recognition of the benefits of small-scale farm anaerobic digesters that valorise on-site wastes for renewable electricity and heat, cushioning agri-businesses against energy perturbations. To explore economic viability of farm-based biogas production, combinations of support levels, energy prices, capital cost, internal rate of return (IRR), and digestate value were analysed, employing a 550-cow dairy farm with access to other agricultural wastes. A 145 kWe system utilising 100% of CHP electricity (grid value: £0.1361 per kWh) and 70% of the heat (heating oil value: £0.055 per kWh) could achieve an IRR above 15.5% with a median electricity tariff of £0.1104 per kWh at a heat tariff from £0.0309 to £0.0873 per kWh thermal. Under a subsidy-free regime, the same system could achieve a 10% IRR with electricity prices in the range £0.149 to £0.261 per kWh. High fertiliser prices could increase digestate value, further improving viability. With late-2021 high energy prices, the technology approaches subsidy-free viability, but uptake is unlikely unless wider environmental and societal benefits of on-farm systems can be explicitly valued.

Recent advances and future directions on the valorization of spent mushroom substrate (SMS): A review

Commercial mushrooms are cultivated on lignocellulose wastes, such as corncob, saw dust, straw and wood chips. Following the rapidly increasing global mushroom production, the efficient recycling and utilization of the by-product, known as spent mushroom substrate (SMS) has garnered much attention due to the serious pollution issues caused. Embracing the concept of 'circular economy', the SMSs have demonstrated immense potential in wide range of applications, including recycling as the substrate for new cultivation cycle of mushroom, biofertilizer and soil amendment, animal feed, renewable energy production and pollution bioremediation. The review provided an overview and recent advances focusing on these applications, analyzed the possible challenges and proposed future directions for sustainable development of global mushroom industry.

Organic waste conversion through anaerobic digestion: A critical insight into the metabolic pathways and microbial interactions

Anaerobic digestion is a promising method for energy recovery through conversion of organic waste to biogas and other industrial valuables. However, to tap the full potential of anaerobic digestion, deciphering the microbial metabolic pathway activities and their underlying bioenergetics is required. In addition, the behavior of organisms in consortia along with the analytical abilities to kinetically measure their metabolic interactions will allow rational optimization of the process. This review aims to explore the metabolic bottlenecks of the microbial communities adopting latest advances of profiling and ¹³C tracer-based analysis using state of the art analytical platforms (GC, GC-MS, LC-MS, NMR). The review summarizes the phases of anaerobic digestion, the role of microbial communities, key process parameters of significance, syntrophic microbial interactions and the bottlenecks that are critical for optimal bioenergetics and enhanced production of valuables. Considerations into the designing of efficient synthetic microbial communities as well as the latest advances in capturing their metabolic cross talk will be highlighted. The review further explores how the presence of additives and inhibiting factors affect the metabolic pathways. The critical insight into the reaction mechanism covered in this review may be helpful to optimize and upgrade the anaerobic digestion system.

Nematocidal activity of hydroalcoholic extracts of spent substrate of Pleurotus djamor on L3 larvae of Haemonchus contortus

The objective of this study was to evaluate and compare the in vitro lethal effect of the hydroalcoholic extract of the spent substrate of Pleurotus djamor ECS-123, obtained at 15 days of colonization (SPS) and at the first (SPS1) and second (SPS2) harvests, against infective larvae L₃ of Haemonchus contortus. The in vitro lethal effect was evaluated by the L₃ larval mortality test (LM) using six concentrations: 1.25, 2.5, 5, 10, 20, and 40 mg/mL, with ivermectin and thiabendazole (5 mg/mL) as controls. The first harvest extract (SPS1) of strain ECS-123 was subjected to liquid-liquid bipartition, which resulted in two fractions: aqueous (PdAcO) and ethyl acetate (PdAct). The chemical fractionation of PdAct with the highest mortality rate (80.11 %) was carried out with open-column chromatography, giving a total of 13 fractions, which were analyzed by thin-layer chromatography (TLC) and grouped into 5 mixtures (R1;1-3, R2;4-7, R3;8-9, R4;10-11 and R5;12-13). Subsequently, the mixtures were evaluated against H. contortus L₃ larvae. Finally, the components of the mixtures with the highest nematocidal effects were evaluated by gas chromatography coupled to mass spectrometry (GC-MS). The data were analyzed with a completely randomized design through ANOVA using the generalized linear model (GLM) with the "R" program. The purification and characterization of R4 and R5 by GC-MS revealed the presence of the following compounds: veratryl alcohol, 4-hydroxy-3,5,5 trimethyl-4-[3-oxo-1-butenyl]-2- cyclohexen-1-one, caffeine and 5,6-dimethoxy-1(3 H) isobenzofuranone. This information allowed for the identification of nematocidal compounds in the degraded substrate of P. djamor, an activity that had not been reported previously.

Bioenergy from dairy manure: technologies, challenges and opportunities

Dairy manure (DM) is a kind of cheap cellulosic biomass resource which includes lignocellulose and mineral nutrients. Random stacks not only leads damage to the environment, but also results in waste of natural resources. The traditional ways to use DM include returning it to the soil or acting as a fertilizer, which could reduce environmental pollution to some extent. However, the resource utilization rate is not high and socio-economic performance is not utilized. To expand the application of DM, more and more attention has been paid to explore its potential as bioenergy or bio-chemicals production. This article presented a comprehensive review of different types of bioenergy production from DM and provided a general overview for bioenergy production. Importantly, this paper discussed potentials of DM as candidate feedstocks not only for biogas, bioethanol, biohydrogen, microbial fuel cell, lactic acid, and fumaric acid production by microbial technology, but also for bio-oil and biochar production through apyrolysis process. Additionally, the use of manure for replacing freshwater or nutrients for algae cultivation and cellulase production were also discussed. Overall, DM could be a novel suitable material for future biorefinery. Importantly, considerable efforts and further extensive research on overcoming technical bottlenecks like pretreatment, the effective release of fermentable sugars, the absence of robust organisms for fermentation, energy balance, and life cycle assessment should be needed to develop a comprehensive biorefinery model.

Anaerobic co-digestion: Current status and perspectives

Anaerobic digestion is a long-established technology for the valorization of diverse organic wastes with concomitant generation of valuable resources. However, mono-digestion (i.e., anaerobic digestion using one feedstock) suffers from challenges associated with feedstock characteristics. Co-digestion using multiple feedstocks provides the potential to overcome these limitations. Significant research and development efforts have highlighted several inherent merits of co-digestion, including enhanced digestibility due to synergistic effects of co-substrates, better process stability, and higher nutrient value of the produced co-digestate. However, studies focused on the underlying effects of diverse co-feedstocks on digester performance and stability have not been synthesized so far. This review fills this gap by highlighting the limitations of mono-digestion and critically examining the benefits of co-digestion. Furthermore, this review discusses synergistic effect of co-substrates, characterization of microbial communities, the prediction of biogas production via different kinetic models, and highlights future research directions for the development of a sustainable biorefinery.

Perspectives on microbial community in anaerobic digestion with emphasis on environmental parameters: A systematic review

This paper review is aiming to comprehensively identify and appraise the current available knowledge on microbial composition and microbial dynamics in anaerobic digestion with focus on the interconnections between operational parameters and microbial community. We systematically searched Scopus, Web of Science, pubmed and Embase (up to August 2019) with relative keywords to identify English-language studies published in peer-reviewed journals. The data and information on anaerobic reactor configurations, operational parameters such as pretreatment methods, temperature, trace elements, ammonia, organic loading rate, and feedstock composition and their association with the microbial community and microbial dynamics were extracted from eligible articles. Of 306 potential articles, 112 studies met the present review objectives and inclusion criteria. The results indicated that both aceticlastic and hydrogenotrophic methanogenesis are dominant in anaerobic digesters and their relative composition is depending on environmental conditions. However, hydrogenotrophic methanogens are more often observed in extreme conditions due to their higher robustness compared to aceticlastic methangoens. Firmicutes and Bacteroidetes phyla are most common fermentative bacteria of the acidogenic phase. These bacteria secrete lytic enzymes to degrade organic matters and are able to survive in extreme conditions and environments due to their spores. In addition, among archaea Methanosaeta, Methanobacterium, and Methanosarcinaceae are found at high relative abundance in anaerobic digesters operated with different operational parameters. Overall, understanding the shifts in microbial composition and diversity as results of operational parameters variation in anaerobic digestion process would improve the stability and process performance.

Strategies to boost anaerobic digestion performance of cow manure: Laboratory achievements and their full-scale application potential

Cow manure represents a surplus manure waste in agricultural food sectors, which requires proper disposal. Anaerobic digestion, in this regard, has raised global interest owing to its apparent environmental benefits, including simultaneous waste diminishment and renewable energy generation. However, dedicated intensifications are necessary to promote the degradation of recalcitrant lignocellulosic components of cow manure. Hence, this manuscript presents a review of how to exploit cow manure in anaerobic digestion through different incentives extensively at lab-scale and full-scale. These strategies comprise 1) co-digestion; 2) pretreatment; 3) introduction of additives (trace metals, carbon-based materials, low-cost composites, nanomaterials, and microbial cultures); 4) innovative systems (bio-electrochemical fields and laser irradiation). Results imply that co-digestion and pretreatment approaches gain the predominance on promoting the digestion performance of cow manure. Particularly, for the co-digestion scenario, the selection of lignin-poor co-substrate is highlighted to produce maximum synergy and pronounced removal of lignocellulosic compounds of cow manure. Mechanical, thermal, and biological (composting) pretreatments generate mild improvement at laboratory-scale and are proved applicable in full-scale facilities. It is noteworthy that the introduction of additives (Fe-based nanomaterials, carbon-based materials, and composites) is acquiring more attention and shows promising full-scale application potential. Finally, bio-electrochemical fields stand out in laboratory trials and may serve as future reactor modules in agricultural anaerobic digestion installations treating cow manure.

Biogas Production from Anaerobic Co-Digestion of Spent Mushroom Substrate with Different Livestock Manure

Spent mushroom substrate (SMS) is defined as the biomass waste generated during industrial mushroom cultivation. Utilization of SMS has been extensively researched and has immense potential as a sustainable substrate for generating biogas that can offset fossil fuel use. This closed loop energy generation process that can be set up in mushroom plants will reduce the dependence on fossil fuels and has the potential to reduce greenhouse gas emissions, which will benefit the environment. Anaerobic co-digestion of SMS with different agricultural wastes such as livestock manure would result in enhanced biogas production. In this study, the anaerobic co-digestion of SMS was carried out by combing yellow back fungus SMS along with chicken, dairy and pig manure. SMS combined with chicken manure yielded a slightly higher cumulative methane yield when compared with the combination of dairy manure and pig manure. Factors such as the total solids (TS) and the relative ratio of manure to SMS loading had a significant impact on the cumulative methane yield, volatile solids removal, with a particularly prominent synergistic effect. The synergistic effect was also closely related to the C/N ratio, and under experimental conditions (TS = 15%, SMS relative ratio of 50% and C/N ratio = 25.6), the cumulative methane yield of SMS with chicken manure (CM) was increased by 414% compared with that obtained using SMS or CM separately. We carried out a multiple linear regression (MLR) analysis, a statistical technique that uses several explanatory variables to predict the outcome of a response variable. Our analysis concluded that by using operating conditions (TS = 15%, and SMS ratio = 38.9), we were able to achieve the maximum cumulative methane yield (CMY).

Comparative analysis of prediction models for methane potential based on spent edible fungus substrate

In this study, ten spent edible fungus (SEF) with different compositional features were used for the maximum methanogenic potential (P₀) evaluation, and the prediction models including regression and kinetics based on this were developed separately. The results showed that the regression model with more chemical components had a good correlation with the P₀, and at least three chemical compositions could reach the threshold of sensitivity. The Cone model showed the best fitting effect on P₀ in all kinetic models, which had higher R-square (>0.994) and lower error (1.004-5.672%). Meanwhile, the minimum digestive testing time (14 days) was determined by the evaluation of sensitivity via statistical indicators. It is concluded that the determination of the prediction model of P₀ should be evaluated with the combination of statistical indicators and specific requirements.

Effects of spent mushroom substrate on the dissipation of polycyclic aromatic hydrocarbons in agricultural soil

Spent mushroom substrate (SMS) is an agricultural waste with a high potential for polycyclic aromatic hydrocarbons (PAH) removal in aged contaminated soils. In this study, fresh and air-dried Pleurotus ostreatus, Pleurotus eryngii, and Auricularia auricular SMSs were used to remove PAHs in agricultural soil under 60-day incubation. The potential of SMS in PAH dissipation was studied by detecting the dissipation rate and the soil physicochemical index, enzyme activity, PAH-degradation bacterial biomass, and microbial diversity. Results showed that SMS significantly enhanced the dissipation of PAHs and fresh SMS had a better effect than air-dried SMS. The highest dissipation rate of 16 PAHs was 34.5%, which was observed in soil amended with fresh P. eryngii SMS, and the PAH dissipation rates with low and high molecular weights were 41.3% and 19.4%, respectively. By comparison, fresh P. eryngii SMS presented high nutrient contents, which promoted the development of PAH-degrading bacteria and changed the soil bacterial community involved in degradation, thereby promoting the PAH dissipation. The lignin-degrading enzymes in fresh SMS were abundant, and the laccase and manganese peroxidase activities in the treatment of fresh P. eryngii SMS was higher than those in other treatments. Fresh P. eryngii SMS improved the relative abundance of Microbacterium, Rhizobium, and Pseudomonas in soil, which were all related to PAH degradation. Consequently, adding fresh P. eryngii SMS was an effective method for remediating aged PAH-contaminated agricultural soils.

Methane yields during anaerobic co-digestion of animal manure with other feedstocks: A meta-analysis

Anaerobic co-digestion of animal manure with other feedstocks (aka co-digestion) is increasingly being used to enhance methane yield and organic waste management. The benefits accruing from co-digestions compared to mono-digestions, however, vary greatly in the literature. The goal of this research was to use meta-analysis to critically compare methane yields between mono- and co-digestions and identify relevant factors (co-substrate type, substrate dose, carbon to nitrogen (C/N) ratio, volatile solids (VS), substrate pH, organic loading rate (OLR), and hydraulic retention time (HRT)) contributing to methane yield. Published studies (n = 64 representing 384 case-studies) with sufficient detail on methane yield were identified for the meta-analysis. Analysis indicated that co-digestion of animal manure with other feedstocks significantly increased methane yield (249 L kg^-1[VS]), compared with anaerobic mono-digestion of animal manure (171 L kg^-1[VS]). Similar methane yields increases (47-57 L kg^-1[VS]) were obtained from co-digestions in batch reactors of swine (238-287 L kg^-1[VS]), poultry (213-260 L kg^-1[VS]), and cattle manure (147-204 L kg^-1[VS]). In continuous digesters of cattle manure (175-299 L kg^-1[VS]) co-digestion had the greatest methane yield improvement of 124 L kg^-1[VS], swine manure (212-322 L kg^-1[VS]) co-digestion ranked second with 110 L kg^-1[VS], and poultry manure ranked third with 70 L kg^-1[VS]. Improved methane yield were obtained at optimum C/N ratio ranging from 26 to 34. The respective optimum OLR for co-digestion of swine, poultry, and cattle manure were 1.2, 1.4 and 3.4 kg VS m^-3 d^-1, while the recommended HRT was 30-40 d. Taken together, anaerobic co-digestion of animal manure with other feedstock significantly improved anaerobic digestion. Factors contributing to methane yields included: substrate-type and dose, VS, C/N, OLR, and HRT.

M. B. Morais A, Freitas AC, C. F. R. Ferreira I, Pintado M. Valorization of Mushroom By-Products as a Source of Value-Added Compounds and Potential Applications

Nowadays, the food sector is highly concerned with environmental issues and foreseen to develop strategies to reduce waste and losses resulting from activities developed in the food system. An approach is to increment added value to the agro-industrial wastes, which might provide economic growth and environmental protection, contributing to a circular economy. Mushroom by-products represent a disposal problem, but they are also promising sources of important compounds, which may be used due to their functional and nutritional properties. Research has been developed in different fields to obtain value added solutions for the by-products generated during mushroom production and processing. Bioactive compounds have been obtained and applied in the development of nutraceutical and pharmaceutical formulations. Additionally, other applications have been explored and include animal feed, fertilizer, bioremediation, energy production, bio-based materials, cosmetics and cosmeceuticals. The main purpose of this review is to highlight the relevant composition of mushroom by-products and discuss their potential as a source of functional compounds and other applications. Future research needs to explore pilot and industrial scale extraction methods to understand the technological feasibility and the economic sustainability of the bioactive compounds extraction and valorization towards different applications.

First report of the nematicidal activity of Flammulina velutipes, its spent mushroom compost and metabolites

The aim of the present work was to evaluate the nematicidal potential of Flammulina velutipes and its spent mushroom compost. Additionally, the nematicidal activity of enzymes and metabolites was analyzed. Isolated F. velutipes and its SMC had significant nematicidal effect on Panagrellus sp. larvae. The percentages of reduction in relation to the control group were: 69, 57.5 and 70% for SMC and 56, 24.5 and 26.6% for the isolated fungus, for 24, 48 and 72 h, respectively. The active SMC crude extract showed nematicidal action with reduction percentages of 43 and 57% for 24 and 48 h of incubation, respectively. The boiled crude extract also showed nematicidal action, however, the reduction percentages were lower than those of the active extract. This demonstrated that the nematicidal action was due to enzyme activities and other metabolites. The results demonstrated that SMC, the isolated fungus, the crude extract and the boiled crude extract showed a significant percentage of reduction on Panagrellus sp. larvae. SMC evidenced a higher nematicidal activity than the isolated fungus. In addition, nematophagous activity of F. velutipes was observed for the first time.

Anaerobic Digestion Technology for Methane Production Using Deer Manure Under Different Experimental Conditions

Anaerobic digestion (AD) is an important technology for the treatment of livestock and poultry manure. The optimal experimental conditions were studied, with deer manure as a fermentation material and mushroom residue as an inoculum. At the same time, methane production was increased by adding zeolite and changing the magnetic field conditions. The results showed that a 6% solid content was the best condition for producing methane. The optimal conditions for methane production were obtained by adding 35 g of mushroom residue to 80 g of deer manure at 35 °C. The addition of organic wastewater (OW) improved methane production. The result of improving the methane production factor showed that adding zeolite during the reaction process could increase the methane production rate. When the amount of zeolite was over 8% total solids (TSes), methane production could improve, but the rate decreased. Setting a different magnetic field strength in the AD environment showed that when the distance between the magnetic field and the reactor was 50 mm and the magnetic field strength was 10–50 mT, the methane production increment and the content of methane in the mixed gases increased.

Valorization of ash and spent mushroom substrate via solid-state solubilization by Acidithiobacillus ferrooxidans

This work describes the possibility of utilization of ash originated from the incineration of sewage sludge from the wastewater treatment plant with the 3rd stage of biological treatment, and spent mushrooms substrate (SMS) as a raw material for the production of the substrate for agriculture and horticulture with the property of slow-releasing of phosphorus via solubilization process. Ash was mixed with SMS in different ratios (1, 5 and 10%), where SMS was used as a substrate/medium - the source of nutrients necessary for the growth of bacteria Acidithiobacillus ferrooxidans (A. ferrooxidans), while the ash was used as a source of phosphorus. Solubilization of phosphorus from ash via solubilization process was conducted for 50 days. During this time pH, conductivity, as well as the concentration of available forms of phosphorus were monitored. Obtained results were compared with the control group deprive inoculation by A. ferrooxidans. The concentration of available to plants phosphorus (express as P₂O₅) was an average 1.5 times higher in the SMS inoculated with A. ferrooxidans in all considered groups. Observation confirms the possibility of utilization of treated SMS as a substrate in agriculture and horticulture as the utilitarian properties (weight and length of plant/root) of plants obtained in germination test were higher when compared with the control group where SMS without inoculation was used.

Development of methanogens within cathodic biofilm in the single-chamber microbial electrolysis cell

The aim of this study was to investigate the development of cathodic biofilm and its effect on methane production in a single-chamber microbial electrolysis cell (MEC). The MEC with 1 g/L acetate was successfully operated within 31 cycles (∼2400 h). The maximum methane production rate and average current capture efficiency in the MEC reached 93 L/m³·d and 82%, respectively. Distinct stratification of Methanobacteriaceae within cathodic biofilm was observed after 9 cycles of operation. The relative abundance of Methanobacteriaceae in the microbial community increased from 45.3% (0-15 μm), 57.6% (15-30 μm), 66.9% (30-45 μm) to 77.2% (45-60 μm) within the cathodic biofilm. The methane production rates were positively correlated with the mcrA gene copy numbers in the cathodic biofilm. Our results should be useful to understand the mechanism of methane and hydrogen production in the MEC.

Spent substrate of Ganodorma lucidum as a new bio-adsorbent for adsorption of three typical dyes

Spent substrate of Ganodorma lucidum (SSGL), waste from cultivation of Ganoderma lucidum, was firstly used as a bio-adsorbent to adsorb three typical dyes malachite green, safranine T and methylene blue, and the adsorption thermodynamics and dynamics were also studied. SSGL was rich of hydroxyl group and carbonyl group, which had the potential to be an efficient bio-adsorbent for the three dyes removal from water and wastewater, and the treatment model should be eco-friendly. The experimental data fit well with the Langmuir and Freundlich isotherm, and the adsorption of dyes took place mainly on monolayer surface of SSGL. The experimental data fit also well with the adsorption thermodynamics, the adsorption were spontaneous and mainly a chemical adsorption. SSGL could adsorb the dyes rapidly and achieve an equilibrium in a short time, and the experimental data fit well with the second-order kinetics model.

Mushroom cultivation in the circular economy

Commercial mushrooms are produced on lignocellulose such as straw, saw dust, and wood chips. As such, mushroom-forming fungi convert low-quality waste streams into high-quality food. Spent mushroom substrate (SMS) is usually considered a waste product. This review discusses the applications of SMS to promote the transition to a circular economy. SMS can be used as compost, as a substrate for other mushroom-forming fungi, as animal feed, to promote health of animals, and to produce packaging and construction materials, biofuels, and enzymes. This range of applications can make agricultural production more sustainable and efficient, especially if the CO₂ emission and heat from mushroom cultivation can be used to promote plant growth in greenhouses.