Lignocellulose-degrading enzymes, free-radical transformations during composting of lignocellulosic waste and biothermal phases in small-scale reactors

Synergistic effect triggered by Fe2O3 and oxygen-induced hydroxyl radical enhances formation of amino-phenolic humic-like substance

Metal oxides play a promising role in the transformation of polyphenols and amino acids involved in naturally occurring humification. The objective of this study was to explore the synergistic interactions between Fe2O3 and O2 in the formation of humic substances under a controlled O2 atmosphere (0%, 21% and 40% O2 levels). The results indicate that an O2 level of 21% with Fe2O3 was optimal for humic acid (HA) production. Hydroxyl radicals (∙OH) formed and promoted the formation of HA in the presence of O2, and O2 improved the enhancing capacity of Fe2O3 by oxidizing Fe(II) to Fe(III). Moreover, the combination of these processes resulted in a synergistic improvement in humification. The evolution of functional groups in HA suggested that O2 promoted the formation of oxygen-containing groups such as lipids, and Fe2O3 was conducive to the formation of dark-coloured polymers during the darkening process of humification. Furthermore, the O2 level of 40% inhibited the formation of HA by reducing the transformation from Fe(III) to Fe(II). The XRD results showed few changes in the composition of Fe2O3 before and after humification, which indicated that Fe2O3 was a catalyst and an oxidant. The heterospectral UV-Vis/FTIR results suggested that ∙OH attacked phenolic rings to form the aromatic ring skeleton of HA and benefit the ring-opening copolymerization of humic precursors. In addition, structural equation modelling demonstrated that dissolved Fe was the key parameter affecting the HA yield. These findings provide new insights into the synergism of O2-mediated ∙OH production associated with metal oxide-facilitated humification.

Effect of inoculating thermophilic bacterial consortia on compost efficiency and quality

The objective of this study was to investigate the potential effects of thermophilic bacterial consortia on compost efficiency and quality. The application of bacterial consortia resulted in an earlier onset of the thermophilic period (THP), an increased upper temperature limit, and an extended duration of the THP by 3-5 days compared to the control group (CK). Microbial inoculation significantly improved the efficiency of organic matter degradation, as well as the content of water-soluble nitrogen (WSN) and humic acid-carbon (HAC). In the case of consortium Ⅱ inoculation (T2), the activities of cellobiohydrolase, β-glucosidase, and protease were increased by 81.81 %, 70.13 %, and 74.09 % at the THP respectively compared to CK. During the maturation stage, T2 also exhibited the highest PV, n/PIII, n value (1.33) and HAC content (39.53 mg·g-1), indicating that inoculation of consortium Ⅱ effectively promoted substrate maturity and product quality. Moreover, this inoculation effectively optimized the bacterial communities, particularly the growth of Planococcus, Chelatococcus, and Chelativorans during the composting, which were involved in carbon and nitrogen conversion or HAC synthesis. Carbohydrate and amino acid metabolism, and membrane transport were predominant in the consortia-inoculated samples, with an increased gene abundance, suggesting that inoculation contributed to promoting the biodegradation of lignocellulose and the exchange of favorable factors. In conclusion, this study demonstrates that inoculating thermophilic bacterial consortia has a positive impact on enhancing the resource utilization efficiency of agricultural waste and improving the quality of compost products.

Effect of diaper waste on composting of household wet biodegradable waste in a decentralized system

Due to changes in lifestyle and improved economic status, the use of diapers is also increasing in developing nations. Hence, there is a need to develop an eco-friendly system for the disposal of discarded diapers which is termed diaper waste (DW). In the present study, the co-composting of DW with household wet biodegradable waste (HWBW) was performed in a compartmentalized rotary drum (CRD) (total capacity = 160 L, number of compartments = 4) under passive aeration conditions. For the co-composting runs, 1 kg of HWBW and DW mixture (mass ratio = 100:0, 90:10, 85:15, and 80:20) was added in four individual compartments daily for 10 days. During the process, the highest temperature of ~ 50-56 °C could be achieved in different compartments for a duration of 2-8 days. The compost yield (i.e., below 4 mm size material) was ranged 10.4-13% after 55 days of composting and the mass of DW was reduced by ~ 61-68%. A mixture of 15% DW and 85% HWBW can be suggested as the best combination for the co-composting process. Based on the "Dewar test" results, the samples recovered after composting could be categorized as "stable". The pot results showed an improvement in the growth of Vigna Radiata when 10% compost sample was mixed with soil whereas with 20% compost in the soil-compost mixture, the plant growth was adversely affected. Hence, co-composting of DW with HWBW can be a feasible proposition which can produce a good quality compost.

Diversity and enzymatic activity of the microbiota isolated from compost based on restaurant waste and yard trimmings

Introduction

The bad management of organic waste negatively affects environmental quality and composting has been a viable recycling alternative. Microorganisms are responsible for waste degradation during the composting process and, consequently, for transforming this waste into natural fertilizer. This work aimed to analyze and identify the biodiversity of yeasts and filamentous fungi throughout a composting process based on organic residues under different treatments (commercial inoculum, non-commercial inoculum, and control treatment) and to investigate the enzymatic activity of these microorganisms.

Methods

Microorganisms were isolated and identified from samples at 0, 5, 10, 20, 40, 60, and 120 days. Filamentous fungi were identified according to their macroscopic and microscopic characteristics, and yeasts were identified by sequencing the 18S rDNA region. All identified strains were evaluated for ligninolytic, cellulolytic, hemicellulolytic, amylolytic, pectinolytic, proteolytic, lipolytic, and ammonification. During the composting phases, the filamentous fungi were higher than the yeast population.

Results and discussion

At the beginning of the process, a higher species diversity was observed, and the population of yeasts and filamentous fungi was, on average, 6.50 log CFU g−1. The microbial communities were similar throughout the process in the two inoculated treatments, which showed more significant microbial activity, diversity, and efficiency in the transformation of organic matter, and consequently, advantages in terms of the final product quality compared to the control treatment. The yeasts Pichia kudriavzevii, Pichia farinosa, Issatchenkia orientalis, and the filamentous fungi of the genus Aspergillus spp. proved to have high biotechnological value and could be used as starter cultures to accelerate the composting process.

Incorporation of Substrates and Inoculums as Operational Strategies to Promote Lignocellulose Degradation in Composting of Green Waste—A Pilot-Scale Study

Composting is a sustainable alternative for green waste (GW) valorization contributing to the circular bioeconomy. However, the processing time must be reduced and the end-product quality must be improved. This study determined the effect of the incorporation of processed food waste (PFW), unprocessed food (UPFW), sawdust (SW), phosphate rock (PR) and a specific bacterial inoculum on GW-composting process parameters and product quality. Three treatments were evaluated in 120 kg piles: (i) TA: (GW + UPFW + PFW + inoculum), (ii) TB (GW + UPFW + PFW), and (iii) TC (GW). An inoculum of Bacillus sp. and Paenibacillus sp. was incorporated in the cooling phase for TA. On the other hand, the effect of the inoculum at the laboratory scale (20 kg reactors) was compared with that found at the pilot scale (120 kg piles). The incorporation of FW, SW, PR and the inoculum increased the amount of lignocellulose biodegradation (TA: 29.1%; TB: 22.7%; TC: 18.2%), which allowed for a reduction of up to 14 days of processing time. The product obtained for TA had a similar quality to the other two treatments, although a lower phytotoxicity was determined according to the germination index (TA: 95%; TB: 85%; and TC: 83%). The final product of TA showed the best agricultural characteristics with pH 8.3, TOC of 24.8%, TN of 1.32%, and GI of 98.8%. Finally, the scaling effect with the bacterial inoculum was shown to affect parameters such as the TOC, TN, GI, and, to a lesser extent, temperature and pH. The results obtained in this paper highlight the importance of optimizing the composting of GW, specifically with the use of co-substrates and specific inocula, which can be of interest for composting materials with a high content of lignocellulose such as GW.

Dynamics of microbiota and physicochemical characterization of food waste in a new type of composter

Organic wastes are considered the most significant components of urban solid waste, negatively affecting the environment. It is essential to use renewable resources to minimize environmental risks. Composting is one of the most sustainable methods for managing organic waste and involves transforming organic matter into a stable and nutrient-enriched biofertilizer, through the succession of microbial populations into a stabilized product. This work aimed to evaluate the efficiency of the new type of composter and the microbial and physiochemical dynamics during composting aiming to accelerate the degradation of organic waste and produce high-quality compost. Two inoculants were evaluated: (1) efficient microorganisms (EM); (2) commercial inoculum (CI), which were compared to a control treatment, without inoculation. Composting was performed by mixing organic waste from gardening with residues from the University's Restaurant (C/N ratio 30:1). The composting process was carried out in a 1 m3 composter with controlled temperature and aeration. The thermophilic phase for all treatments was reached on the second day. Mature compost was obtained after an average of 120 days, and composting in all treatments showed an increase in the availability of P and micronutrients. The new composter helped to accelerate the decomposition of residues, through the maintenance of adequate oxygen content and temperature control inside the cells, providing high metabolic activity of microorganisms, contributing to an increase in physicochemical characteristics, also reducing the composting time in both treatments. During composting, the bacteria and actinobacteria populations were higher than yeasts and filamentous fungi. The inoculated treatments presented advantages showing more significant mineralization of P-available and micronutrients such as Mn and Zn in terms of the quality of the final product in comparison to the control treatment. Finally, the new composter and the addition of inoculants contributed significantly to the efficiency of the process of composting organic waste.

Deciphering the effect of exogenous lignocellulases addition on the composting efficiency and microbial communities

This study aimed to reveal the potential effects of exogenous lignocellulases addition on the composting efficiency and microbial communities. The lignocellulases addition at the mesophilic phase (MEP) greatly expedited the substrate conversion and the rise of temperature at the initial stage, driving the early arrival of thermophilic phase (THP), caused by the positive effects of Sphingobacterium and Brevundimonas. When being added at the THP, the potential functions and interactions of microbial communities were stimulated, especially for Thermobispora and Mycothermus, which prolonged the duration of the THP and expedited the humic acid formation. Simultaneous addition (MEP and THP) significantly altered the microbial community succession and activated the microbes that contributed to the lignocellulases secretion, exhibiting the highest cellobiohydrolase (36.19 ± 3.25 U· g^-1 dw) and xylanase (47.51 ± 3.32 U·g^-1 dw) activity at the THP. These findings provide new strategies that can be effectively utilized to improve the efficiency and quality of composting.

Optimization of lignocellulolytic bacterial inoculum and substrate mix for lignocellulose degradation and product quality on co-composting of green waste with food waste

The present study evaluates the effect of the mixing ratio of substrates and inoculation with lignocellulolytic bacteria on green waste (GW) and food waste (FW) co-composting. A Box-Behnken design was used to simultaneously optimize the lignocellulose degradation (%LD) and end-product quality. The best operational conditions were 4.85*10⁵ CFU g^-1 of Bacillus sp. F3X3 and 1.44*10⁶ CFU g^-1 of Paenibacillus sp. F1A5 with a substrate mixture containing 50% GW, 32.5% unprocessed FW, 2.5% processed FW, 13% sawdust, and 2% phosphate rock; with a C/N ratio of 27. Under these conditions, the %LD was 33% and the end-product has pH 8.3, TOC 22,4%, TN 1,7%, and a germination index of 103%. Therefore, the product complies with quality standards for organic fertilizers. The results of this study allow the identification of appropriate strategies to optimize GW composting, increasing the degradation of lignocellulose and improving the end-product quality.

Optimization of Conditions for Feather Waste Biodegradation by Geophilic Trichophyton ajelloi Fungal Strains towards Further Agricultural Use

The aim of the study was to optimize culture conditions and medium composition to accelerate the biodegradation of chicken feather waste by keratinolytic soil strains of Trichophyton ajelloi, which are poorly known in this respect, as well as to propose hitherto unconsidered culture conditions for these fungi in order to obtain a biopreparation with a high fertilization value. Different pH of the medium, incubation temperatures, amounts of chicken feathers, additional carbon sources, and culture methods were tested. The process of optimizing keratin biodegradation was evaluated in terms of measuring the activity of keratinase, protease, disulfide reductase, concentration of released soluble proteins and peptides, total pool of amino acids, ammonium and sulfate ions, changes in medium pH, and feather weight loss. It was found that the studied fungal strains were capable of decomposing and mineralizing keratin from feather waste. Regarding the fertilizer value of the obtained hydrolysates, it was shown that the release of sulfate and ammonium ions was highest in a stationary culture containing 2% feathers with an initial pH of 4.5 and a temperature of 28 °C. Days 14-21 of the culture were indicated as the optimal culture time for these fungi to obtain biopreparations of high fertilizing value.

Production of pine sawdust biochar supporting phosphate-solubilizing bacteria as an alternative bioinoculant in Allium cepa L., culture

We produced and characterised biochar made from Caribbean pine sawdust as raw material. The biochar (BC₅₀₀) was used as biocompatible support to co-inoculate phosphate solubilizing bacteria (PSB) (BC₅₀₀/PSB) on Allium cepa L., plants at a greenhouse scale for four months. The three biomaterials study included proximate analysis, elemental analysis, aromaticity analysis, scanning electron microscopy, Fourier transform infrared spectroscopy (FTIR), adsorption studies at different pH and PSB stability as a function of time. The results indicated that BC₅₀₀ is suitable as organic support or solid matrix to maintain the viability of PSB able to solubilise P from phosphate rock (PR). The biofertilizer (BC₅₀₀/PSB) allows increasing germination, seedling growth, nutrient assimilation, and growth of Allium cepa L., because PSB immobilised on BC₅₀₀ promoted nutrient mobilisation, particularly P, during cultivation of Allium cepa L., at pots scale. The two treatments to evaluate the biofertilizer (BC₅₀₀/PSB) showed the highest concentrations of total P with 1.25 ± 0.13 and 1.38 ± 0.14 mg bulb^-1 in A. cepa L. This work presents the benefits of a new product based on bacteria naturally associated with onion and an organic material (BC₅₀₀) serving as a bacterial carrier that increases the adsorption area of highly reactive nutrients, reducing their leaching or precipitation with other nutrients and fixation to the solid matrix of the soil.

High tolerance and degradation of fungicides by fungal strains isolated from contaminated soils

The aim of this work was to isolate fungal strains from phytotoxic agricultural soils, screen them, categorize the most tolerant fungi to three fungicides, and identify them by a molecular approach. In this study, 28 fungal strains were isolated from phytotoxic agricultural soil with intensive use of pesticides. The capacity of fungi to resist and degrade different concentrations of carbendazim, captan, and zineb was determined by an exploratory multivariate analysis. Actinomucor elegans LBM 239 was identified as the most tolerant fungus to these fungicides, degrading a 86.62% of carbendazim after 7 days of treatment. In conclusion, A. elegans LBM 239 demonstrated the highest tolerance and capacity to biodegrade carbendazim, becoming a potential candidate for bioremediation of contaminated soils with carbendazim, captan, or zineb.

Effects of Microbial Inoculation with Different Indigenous Bacillus Species on Physicochemical Characteristics and Bacterial Succession during Short-Term Composting

Bacillus accelerates lignocellulose degradation, promotes the stabilization and resource utilization of compost by secreting enzymes, and plays an important role in compost formation and quality control. This study evaluated enzyme activity, lignocellulosic degradation, and bacterial succession in composting inoculated with different microbial Bacillus agents. They were identified as B. licheniformis, B. subtilis, B. thermoamylovorans, B. thermoruber, and B. hisashii. Four treatments were established, including a CK (uninoculated microorganisms), A (B. licheniformis, B. subtilis, B. thermoamylovorans,and B. hisashii), B (B. subtilis, B. thermoamylovorans, B. thermoruber, and B. hisashii), and C (B. subtilis, B. thermoamylovorans, and B. hisashii), and the composting lasted 7–14 days. Lignin and cellulose degradation rates in B during composting were 17.1% and 36.7% at the cooling stage, respectively. Redundancy analysis showed that degradation of lignocellulose in the thermophilic stage was mainly related to the secretion of lignocellulose-degrading enzymes after microbial inoculation. 16S rRNA sequencing revealed that Bacillus (20.3%) and Thermobifida (20.2%) were the dominant genera. Inoculation with a combination including B. thermoruber was a feasible way to increase lignocellulose degradation and promote maturity in sewage sludge composting.

Deciphering the dominant components and functions of bacterial communities for lignocellulose degradation at the composting thermophilic phase

The decomposition and transformation of organic matters during composting process are performed by various microorganisms. However, the bacterial communities and their functions usually vary with composting materials. Here the dominant bacterial genera and their functions were identified at the thermophilic phase during composting of mulberry branches with silkworm excrement (MSE), pig manure (MPM) and cow manure (MCD). The activities of β-glucosidase and endoglucanase were highest for MCD (1.31 and 17.15 µg g^-1 min^-1) and lowest for MPM (0.92 and 14.22 µg g^-1 min^-1). Random Forest model and correlation analysis revealed that Stenotrophomonas, Bacillus, and Sinibacillus were the dominant bacterial genera involved in lignocellulose degradation regardless of composting materials. Carbohydrate metabolism, amino acid metabolism, and DNA replication and repair were primary functions of the bacterial communities for the three types of composting. The quantification of lignocellulose degradation genes further verified the dominant functions of the bacterial communities.

Biological Indicators of Soil Quality under Different Tillage Systems in Retisol

Soil microorganism diversity has a close relation with soil function, and the changes in the composition of the soil microbial population can directly affect it. The aim of this study was to identify the bacterial community composition and determine the main soil chemical and physical properties formed by the different tillage systems. In the experiment, we analyzed the combination of three tillage systems and four organic fertilizers. Soil samples were taken from the two layers of the soil profile: the upper 0–10 cm and the lower 10–20 cm. The composition and diversity of soil bacterial communities were assessed by the sequencing of 16S rRNA genes. Results revealed that the highest biodiversity was found in the soil with shallow ploughless tillage and enriched with farmyard manure. Actinobacteria and Proteobacteria were the dominant bacterial species across all treatments. Their total abundance varied between 26% and 36% in the different analyzed agroecosystems. For the Dystric Bathygleyic Glossic Retisol, shallow ploughless tillage is the most suitable tillage system, as it creates favorable conditions for the accumulation of organic carbon in the soil under the Western Lithuania climate conditions.

Effects of multi-phase inoculation on the fungal community related with the improvement of medicinal herbal residues composting

Composting has become the most important way to recycle medicinal herbal residues (MHRs). The traditional composting method, adding a microbial agent at one time, has been greatly limited due to its low composting efficiency, mutual influence of microbial agents, and unstable compost products. This study was conducted to assess the effect of multi-phase inoculation on the lignocellulose degradation, enzyme activities, and fungal community during MHRs composting. The results showed that multi-phase inoculation treatment had the highest thermophilic temperature (68.2 °C) and germination index (102.68%), significantly improved available phosphorus content, humic acid, and humic substances concentration, accelerated the degradation of cellulose and lignin, and increased the activities of cellulase in the mature phase, xylanase, manganese peroxidase, and utilization of phenolic compounds. Furthermore, the non-metric multi-dimensional scaling showed that the composting process and inoculation significantly influenced fungal community composition. In multi-phase inoculation treatment, Thermomyces in mesophilic, thermophilic, and mature phase, unclassified_Sordariales, and Coprinopsis in mature phase were the dominant genus that might be the main functional groups to degrade lignocellulose and improve the MHRs composting process.

Microbial succession and degradation during kitchen waste biodrying, highlighting the thermophilic phase

Biodrying in conjunction with compound stone amendment was used to treat kitchen waste, which improved biodrying. After 16 days, the pile moisture content decreased from 68.8% to 23.0%. Lignin, cellulose and hemicellulose concentrations decreased from 104.6 mg g^-1 d.b., 322.9 mg g^-1 d.b. and 155.9 mg g^-1 d.b., respectively, to 74.0 mg g^-1 d.b., 224.8 mg g^-1 d.b. and 134.5 mg g^-1 d.b., respectively. The Shannon index for bacteria increased from 2.5 to 3.1, while for fungi, it decreased from 4.6 to 0.6. The relative abundances of Amino Acid Metabolism and Carbohydrate Metabolism exceeded 7%. The thermophilic phase during the process inactivated the pathogenic microorganisms, increased the bacterial diversity, decreased the fungal diversity, and potentially improved the metabolism of nutrients, including amino acids, carbohydrates, lipids and vitamins. The biomarker analysis and predicated protein sequences provide genetic evidence to elucidate why the thermophilic phase is the peak time for nutrient metabolism.

Possibility to Biotransform Anthracyclines by Peroxidases Produced by Bjerkandera adusta CCBAS 930 with Reduction of Geno- and Cytotoxicity and Pro-Oxidative Activity

The aim of this study was to evaluate the bioremoval mechanism of anthracycline antibiotics by the white-rot fungus B. adusta CCBAS 930. The activity of oxidoreductases and levels of phenolic compounds and free radicals were determined during the biotransformation of anthraquinone antibiotics: daunomycin (DNR) and doxorubicin (DOX) by B. adusta strain CCBAS 930. Moreover, phytotoxicity (Lepidium sativum L.), ecotoxicity (Vibrio fischeri), genotoxicity and cytotoxicity of anthraquinone dyes were evaluated before and after biological treatment. More than 80% and 90% of DNR and DOX were removed by biodegradation (decolorization). Initial solutions of DNR and DOX were characterized by eco-, phyto-, geno- and cytotoxicity. Despite efficient decolorization, secondary metabolites, toxic to bacteria, formed during biotransformation of anthracycline antibiotics in B. adusta CCBAS 930 cultures. DNR and DOX metabolites did not increase reactive oxygen species (ROS) production in human fibroblasts and resazurin reduction. DNR metabolites did not change caspase-3 activity.

Modification of post-industrial lignin by fungal strains of the genus Trichoderma isolated from different composting stages

One of the links in the environmental management chain is the environmentally friendly utilization of the emerging post-industrial waste and improvement of the methods of processing thereof. The aim and novelty of this research was to evaluate the potential of fungi to purify wastewater containing post-industrial lignin, i.e. waste originating from the pulp and paper industry. Trichoderma were dominant in the composts with different qualities and quantities of lignocellulosic compounds. The Trichoderma strains used in the research were isolated from two lignocellulosic composts at three different time points (from 10-, 20- and 30-week-old composting mass). Eighteen strains of the genus Trichoderma were tested for their ability to biodegrade 0.2% post-industrial lignin. It was evaluated by determination of decolorization, activities of ligninolytic enzymes, and concentration of phenolic compounds in the post-culture liquid. The Trichoderma strains isolated from 10-week-old compost I and 30-week-old compost II showed the highest decolorization activity and biotransformation of dark post-industrial lignin. All strains secreted horseradish-like peroxidase (HRP-like), superoxide dismutase-like (SOD-like), xylanase, and phenolic compounds. Strains isolated from 30-week-old compost I and from 10-week-old compost II released the greatest amounts of phenolic compounds into the culture liquid containing post-industrial lignin. The strains isolated from 10- and 20-week-old compost were characterized by high SOD-like and HRP-like activity, respectively. The concentration of phenolic compounds measured with HPLC in Trichoderma fungus culture VII from compost I corresponded with the decolorization degree and high HRP-like activity. The study results indicate that the genus Trichoderma with decolorization activity isolated from the first composting stages can be used in the biotransformation of post-industrial lignin waste.

Improved lignocellulose degradation efficiency based on Fenton pretreatment during rice straw composting

This study aims to explore the effect of Fenton pretreatment on organic fractions, enzymes activities and microbial communities during composting. In this study, rice straw was chosen to be composted after pretreatment. The results indicated that Fenton pretreatment significantly increased the degradation of organic matter and coarse fiber contents, which might be the reason that Fenton pretreatment enhanced lignocellulose-degrading enzymes activities during composting, including CMCase, FPase, xylanase, manganese peroxidase, lignin peroxidase and laccase. Additionally, Fenton pretreatment reshaped bacteria community. The key enzymes and environmental factors, which affected organic fractions degradation were identified by redundancy analysis. Furthermore, structural equation modeling and variation partitioning analysis further revealed possible mechanisms of organic fractions degradation in different treatments during composting. In summary, the combined application Fenton pretreatment and composting improved lignocellulose degradation efficiency, which provided for an effective and environment-friendly way to manage lignocellulose wastes.

Degradation mechanism of lignocellulose in dairy cattle manure with the addition of calcium oxide and superphosphate

Cellulose and lignin belongs to refractory organic matters in the traditional composting. In this research, the degradation of lignocellulose in dairy cattle manure was investigated through adding calcium oxide (CaO) and superphosphate (SSP). In the presence of CaO and SSP, the degradation rate of cellulose and lignin were improved by 25.0% and 8.33%, respectively. The results indicated that the pH value in system would be slightly higher with the addition of CaO and SSP. Besides, the pH value of all cow manure piles were about 8.4 after composting rotten, which could be well neutralized by the gradually acidified soil in the southwest of China with the full effect of fertilizer released. In addition, the abundance of Bacillales, Actinomycetes, and Thermoactinomycetaceae in the experimental groups (AR) was slightly better than that in the control groups (CK) during composting, which led to a conclusion that an elaborate physical-chemical-multivariate aerobic microorganism evolution model of cellulose degradation products (PCMC) was deduced and the physical-chemical-multivariate aerobic microorganism model of lignin cycle degradation (PCML) was developed.

Evolutions of different microbial populations and the relationships with matrix properties during agricultural waste composting with amendment of iron (hydr)oxide nanoparticles

This study investigated the evolutions of different microbial populations and multivariate relationships between their abundances and environmental variables during composting with amendment of Fe (hydr)oxide nanoparticles. Piles treated with nanohematite and nanomagnetite were denoted as T-nanohematite and T-nanomagnetite, and another one was T-control. It was found that nanohematite more effectively increased bacteria and fungi abundances with 1.24∼1.58 times average value of T-control, while nanomagnetite was more useful to actinomycetes. As the most significant variable, the total effect of temperature in T-control and T-nanomagnetite was increased to 0.87 and 0.92, respectively, because both the direct and indirect effects were positive, while it in T-nanohematite was reduced to 0.18 by the negative indirect effect. Partial redundancy analysis suggested that each microbial abundance shared different relationships with composting parameters. Overall, actinomycetes was more sensitive to changes of composting parameters than bacteria and fungi.

Evaluation of the effectiveness of land reclamation based on microbiological and biochemical parameters assessed in an ozokerite mining and processing landfill sown with Trifolium hybridum and Dactylis glomerata

The aim of the study was to analyse the microbiological and biochemical activity of a reclaimed landfill produced during extraction and processing ozokerite and sown with Trifolium hybridum and Dactylis glomerata. The analyses were carried out in the third year after application of two doses of sewage sludge, spent mushroom substrate, sawdust, and manure to the landfill soil. The following parameters were determined: the total number of oligotrophic bacteria and filamentous fungi, the number of cellulolytic and lipolytic bacteria and fungi, respiratory activity, the activity of dehydrogenases, β-glucosidase, and lipase, and the activity of fluorescein diacetate hydrolysis. The results indicated that the wastes exerted a generally positive effect on the microbiological, biochemical, and enzymatic activities analysed in the reclaimed ground sown with both Trifolium hybridum and Dactylis glomerata. There was a negative effect on the total number of bacteria with low nutritional requirements, the number of cellulolytic bacteria, the number of lipolytic fungi, and the β-glucosidase and lipase activities only in some objects. The strength of the effects was dependent on the type and dose of the waste and on the plant species. The strongest impact on the analysed parameters was exerted by the manure, sewage sludge, and spent mushroom substrate, whereas the addition of sawdust was found to be the least beneficial. The higher dose of manure and the lower dose of spent mushroom substrate were the most beneficial doses of the wastes. The number of lipolytic bacteria and cellulolytic bacteria and fungi, as well as the fluorescein hydrolytic activity followed by the activity of dehydrogenases, β-glucosidase, and lipase were the most sensitive parameters.

Establishing the oxidative tolerance of Thermomyces lanuginosus xylanase

AIMS

This work aims to determine the tolerance of xylanase towards enzyme-generated oxidative conditions, such as those produced by the peroxidase or laccase mediator systems (LMS).

METHODS AND RESULTS

The activity of Thermomyces lanuginosus xylanase was measured after incubation with lignin peroxidase, manganese peroxidase or laccase plus various mediators. The laccase system, using mediators such as 1-hydroxybenzotriazole and violuric acid, resulted in complete loss of xylanase activity, accompanied by an increase in the solution potential. However, an increase in solution potential alone was not sufficient to inactivate xylanase, nor was loss of xylanase activity always accompanied by a significant increase in solution potential, as observed with N-hydroxyphthalimide as the mediator. Neither lignin peroxidase nor manganese peroxidase impacted xylanase activity; only extended treatment with elevated hydrogen peroxide concentration promoted modest xylanase activity loss. The mechanism of inactivation as determined by the tryptophan-modifying reagent N-bromosuccinimide (NBS) indicated that oxidation of just one of the eight tryptophan residues of T. lanuginosus xylanase would be sufficient to result in complete loss of xylanase activity, since xylanase is completely inactivated at 1 : 1 molar ratio of NBS to xylanase.

CONCLUSIONS

While showing tolerance to peroxidase-based enzyme systems, T. lanuginosus xylanase is readily inactivated in the presence of the LMS. Based upon treatment with NBS as the oxidant, inactivation can be attributed to modification of a single tryptophan residue.

SIGNIFICANCE AND IMPACT OF THE STUDY

The simultaneous application of mixed hydrolytic and oxidative enzyme systems is of importance to biomass processing industries. Understanding the tolerance of xylanase to oxidative conditions will facilitate the design of reaction conditions or enzyme variants to maximize the impact of mixed enzyme systems.

Changes in mineral forms of nitrogen and sulfur and enzymatic activities during composting of lignocellulosic waste and chicken feathers

The aim of this study was to show the dynamics of changes in the activity of enzymes responsible for C, N, and S metabolism, i.e., cellulase, protease, urease, and arylsulfatase in two lignocellulosic composts as well as changes in the concentration of mineral forms important in plant nutrition (N-NH₄⁺, N-NO₃^-, S-SO₄^2-). Most of the enzyme activity was higher during 10 weeks of composting in compost I, containing higher amounts of easily available organic matter than in compost II. Enzymatic activities in compost II remained at a higher level for a longer time, but they increased at a slower rate. Mineral content changes in the compost mass consisted primarily of an increase in N-NO₃^- concentration and a decrease in N-NH₄⁺ and S-SO₄^2- levels, especially in compost I. The concentration of mineral nitrogen and sulfur forms in compost water extracts was about 10-100 times lower than in the compost mass. At the end of composting, the amount of sulfates in the compost mass was 30 and 150 mg kg^-1 dw in compost II and I, respectively. In this context, the composts obtained should be considered valuable for fertilizing soils poor in this component and for cultivating plants with high sulfate S demand.

Wastewater cleanup using Phlebia acerina fungi: An insight into mycoremediation

The scarcity of available drinking water has led the researchers to develop novel and cost-effective ways of bioremediation process for wastewater treatment. Bioremediation is a cost-effective and environmentally sound method for the removal of toxic compounds. Such approach is not only a chemical-less effort but also an energy savior. In the present work Phlebia acerina, a white rot wood rotting fungi have been used to degrade the toxic wastewater pollutants. Congo Red (CR) and Eriochrome Black T (EBT) have been selected as model pollutants to test the wastewater cleaning ability of the fungus. The Lignin modifying enzyme (LME) and Cellulolytic enzyme assays (CMC) potential of Phlebia acerina helped in understanding the dye degradation mechanism. Under the optimum conditions, the fungi was able to degrade as high as 92.4% CR while the EBT was degraded to a maximum of 50%. Phlebia acerina was found to show first-order kinetics of dyes degradation. Further, the seed germination and antimicrobial assay of treated and untreated water were carried out in order to establish the formation of non-toxic end product after degradation.

Fermentation performance optimization in an ectopic fermentation system

Ectopic fermentation systems (EFSs) were developed for wastewater treatment. Previous studies have investigated the ability of thermophilic bacteria to improve fermentation performance in EFS. Continuing this research, we evaluated EFS performance using principle component analysis and investigated the addition of different proportions of cow dung. Viable bacteria communities were clustered and identified using BOX-AIR-based repetitive extragenic palindromic-PCR and 16S rDNA analysis. The results revealed optimal conditions for the padding were maize straw inoculated with thermophilic bacteria. Adding 20% cow dung yielded the best pH values (6.94-8.56), higher temperatures, increased wastewater absorption, improved litter quality, and greater microbial quantities. The viable bacteria groups were enriched by the addition of thermophilic consortium, and exogenous strains G21, G14, G4-1, and CR-15 were detected in fermentation process. The proportion of Bacillus species in treatment groups reached 70.37% after fermentation, demonstrating that thermophilic bacteria, especially Bacillus, have an important role in EFS, supporting previous predictions.

Microbial strategies and biochemical activity during lignocellulosic waste composting in relation to the occurring biothermal phases

Typically, hardly-degradable lignocellulosic waste is a component or a co-component of the composted mass. The aim of the work was to present the dynamics and succession of microbial communities during small temperature changes, conditioned by the availability of lignocellulosic polymer and feather waste (the presence of N) in composts with qualitatively and quantitatively different lignocellulosic waste, but most of all, to draw attention to the previously not considered microbial strategies in the composted mass. Decomposition of lignocellulose during composting was similar to the priming effect in the soil, because it was associated with the successive occurrence of two groups of microorganisms. The first group of microorganisms, using easily accessible fraction of the lignocellulose complex, was named the first-strategist group, i.e., non-nutritionally specialized group of microorganisms. The second group, utilizing the hard-to-degrade fraction of lignocellulose, was named second-strategist microorganisms, i.e., nutritionally-specialized group of microorganisms. Biodegradation of the lignocellulose complex in compost I enriched with grass (42.86% pine bark, 34.28% grass, 20.0% sawdust and 2.86% chicken feathers) was faster than in compost II that did not contain any grass, but included more hardly degradable components (25.54% pine bark, 10.63% wheat straw, 51.07% sawdust, 12.76% chicken feathers). In compost I, a higher temperature in the thermophilic phase was recorded; larger amounts of non-specialized mesophilic and thermophilic bacteria in the first weeks of composting and a higher abundance of ligninolytic, xylanolytic fungi and cellulolytic bacteria were observed already in biothermal phase 3 with limited access to easily available C and energy sources. During this period, phosphatase, dehydrogenase and respiratory activities were higher in compost I than compost II. This work demonstrates that the succession of particular groups of microorganisms may help determine the start of biodegradation of recalcitrant ligninocellulosic components during composting.

Using cow dung and spent coffee grounds to enhance the two-stage co-composting of green waste

The objective of this study was to determine the effects of cow dung (CD) (at 0%, 20%, and 35%) and/or spent coffee grounds (SCGs) (at 0%, 30%, and 45%) as amendments in the two-stage co-composting of green waste (GW); the percentages refer to grams of amendment per 100g of GW based on dry weights. The combined addition of CD and SCGs improved the conditions during co-composting and the quality of the compost product in terms of composting temperature; particle-size distribution; mechanical properties; nitrogen changes; low-molecular weight compounds; humic substances; the degradation of lignin, cellulose, and hemicellulose; enzyme activities; the contents of total Kjeldahl nitrogen, total phosphorus, and total potassium; and the toxicity to germinating seeds. The combined addition of 20% CD and 45% SCGs to GW resulted in the production of the highest quality compost product and did so in only 21days.

Performance assessment of improved composting system for food waste with varying aeration and use of microbial inoculum

Wet waste recycling at generation point will alleviate burden on the overflowing waste dumpsites in developing nations. Drum composting is a potential treatment option for such waste at individual or community level. The present study was aimed to produce compost from wet waste (primarily comprising food waste) in composting drums modified for improved natural air circulation. Effect of microbial inoculum and waste turning on composting process was also studied. The final results showed the production of matured and stable compost in the modified drums. Addition of the microbial inoculum resulted in thermophilic phase within a week time. The self-heating test and germination index (>80%) showed the production of non-phytotoxic and mature compost in the modified drums after 60days. The change in microbial population, humic substances and biological parameters (lignin, cellulose and hemicellulose) during the study is discussed. Moreover, the reduction in waste mass and volume is also reported.