Influence of Phanerochaete chrysosporium on microbial communities and lignocellulose degradation during solid-state fermentation of rice straw

Effective microorganisms input efficiently improves the vegetation and microbial community of degraded alpine grassland

Soil beneficial microorganism deficiency in the degraded grasslands have emerged as the major factors negatively impacting soil quality and vegetation productivity. EM (effective microorganisms) has been regarded as a good ameliorant in improving microbial communities and restoring degraded soil of agricultural systems. However, knowledge was inadequate regarding the effects of adding EM on the degraded alpine grassland. Four levels of EM addition (0, 150, 200, 250 mL m-2) were conducted to investigate the effects of EM addition on soil properties and microorganisms of degraded alpine grassland. The addition of EM increased aboveground biomass, soil organic carbon, total nitrogen, available phosphorus, and microbial biomass, but decreased soil electric conductivity. Meanwhile, the relative biomasses of gram-negative bacteria decreased, while the ectomycorrhizal fungi and arbuscular mycorrhizal fungi increased after EM addition. The relationship between microbial communities and environmental factors has been changed. The restore effect of EM increased with the increase of addition time. These results indicated that EM addition could be a good practice to restore the health of the degraded alpine grassland ecosystem.

Biochar reinforced the populations of cbbL-containing autotrophic microbes and humic substance formation via sequestrating CO2 in composting process

The quality of compost is drastically reduced due to the loss of carbon, which negatively impacts the environment. Carbon emission reduction and carbon dioxide (CO₂) fixation have attracted much attention in composting research. In this study, the relationship between CO₂ emission, humic substances (HS) formation and cbbL-containing autotrophic microbes (CCAM) was analyzed by adding biochar during cow manure composting. The results showed that biochar can facilitate the degradation of organic matter (OM) and formation of HS, as well as reinforce the diversity and abundance of CCAM community, thereby promoting CO₂ fixation and reducing carbon loss during composting. High-throughput sequencing analysis revealed significant increase in Actinobacteriota and Proteobacteria abundance by 30.97 % and 10.48 %, respectively, thus increasing carbon fixation by 32.07 %. Additionally, Alpha diversity index increased significantly during thermophilic phase, while Shannon index increased by 143.12 % and Sobs index increased by 51.62 %. Redundancy analysis (RDA) indicated that CO₂ was positively correlated with C/N, temperature, HS and dissolved organic matter (DOM), while the abundance of Paeniclostridium, Corynebacterium, Bifidobacterium, Clostridium, Turicibacter and Romboutsia were positively correlated with temperature, CO₂, C/N and E₂/E₄ (p <  0.01).

The white-rot fungus, Phanerochaete chrysosporium, under combinatorial stress produces variable oil profiles following analysis of secondary metabolites

AIMS

The effects of combinatorial stress on lipid production in Phanerochaete chrysosporium remain understudied. This species of white-rot fungi was cultivated on solid-state media while under variable levels of known abiotic and biotic stressors to establish the effect upon fungal oil profiles.

METHODS AND RESULTS

Environmental stressors induced upon the fungus included the following: temperature, nutrient limitation and interspecies competition to assess impact upon oil profiles. Fatty acid type and its concentration were determined using analytical methods of gas chromatography and mass spectrometry. Growth rate under stress was established using high-performance liquid chromatography with ergosterol as the biomarker. Fungi grown on solid-state agar were able to simultaneously produce short- and long-chain fatty acids which appeared to be influenced by nutritional composition as well as temperature. Addition of nitrogen supplements increased the growth rate, but lipid dynamics remained unchanged. Introducing competition-induced stress had significantly altered the production of certain fatty acids beyond that of the monoculture while under nutrient-limiting conditions. Linoleic acid concentrations, for example, increased from an average of 885 ng μl^-1 at monoculture towards 13 820 ng μl^-1 at co-culture, following 7 days of incubation.

CONCLUSIONS

Interspecies competition produced the most notable impact on lipid production for solid-state media cultivated fungi while the addition of nitrogen supplementation presented growth and lipid accumulation to be uncorrelated. Combinatorial stress therefore influences the yield of overall lipid production as well as the number of intermediate fatty acids produced, deriving similar oil profiles to the composition of vegetable and fish oils.

SIGNIFICANCE AND IMPACT OF THE STUDY

Fungal secondary metabolism remains highly sensitive following combinatorial stress. The outcome impacts the research towards optimizing fungal oil profiles for biomass and nutrition. Future investigations on fungal stress tolerance mechanisms need to address these environmental factors throughout the experimental design.

Soil microbial community shifts with long-term of different straw return in wheat-corn rotation system

Despite the integral role of the soil microbial community in straw decomposition, we still have a limited understanding of the complex response of microbial community to long-term of crop straw return in rotation system. Here we report on the structural and functional response of the soil bacterial and fungal community to more than 10 years of straw return in wheat-corn rotation system. Compared with single-season straw return, soil microbial phosphor lipid fatty acids (PLFAs) and catabolic activity were improved more greatly with double-season straw return. The relative abundance of bacteria and fungi decreased with double-season straw return, but increased with single-season straw return. The copiotrophic bacteria were more represented in the soils with corn straw return, while oligotrophic groups were more represented in soils with wheat straw return. Compared with wheat straw return, lower fungal community diversity and higher abundance of fungal pathogen (identified to be Leptosphaeria) were observed with corn straw return, especially at high return rates. Redundancy analysis showed that soil available potassium (P = 0.008) and ratio of C to N (P = 0.048) significantly affected the soil bacterial community, while soil electric conductivity (P = 0.04) was the significant factor impacting soil fungal community. It suggests that full corn straw return might have positive impact on soil mineral nutrient but negative impact on soil fungal community diversity and pathogenic risk, mainly due to the change in soil electric conductivity.

Changes of heavy metal fractions during co-composting of agricultural waste and river sediment with inoculation of Phanerochaete chrysosporium

The effects of Phanerochaete chrysosporium on the bioavailability of multiple heavy metals (Pb, Cd, Cu, and Zn) in river sediments were investigated by co-composting with the agricultural waste. The results showed that the Phanerochaete chrysosporium inoculation can greatly enhance the passivation on Cu, Pb and Cd during 60 days co-composting. The effects in the three metals followed the order: Cu > Cd > Pb. There were no differences for Zn whether inoculation with P. chrysosporium or not. Redundancy analysis (RDA) implied that more than 4/5 of the variation of all fractions data for all heavy metals was explained by all significant canonical axes. P. chrysosporium can change the significant parameters for each metal and enhance the explanatory power of RDA model. The inoculation can strengthen the effect of OM (organic matter) on the bioavailability of heavy metals, but weaken the contribution of pH.

Long-term decomposed straw return positively affects the soil microbial community

AIMS

In order to understand the response of soil microbial communities to the long-term of decomposed straw return, the modifications of soil microbial community structure and composition induced by more than 10 years of fresh and decomposed straw return was investigated and the key environmental factors were analysed.

METHODS AND RESULTS

Phospholipid fatty acid analysis and high-through sequencing technique were applied to analyse the structure and composition of the soil microbial communities. Compared with fresh straw, returning decomposed straw increased the relative abundance of bacteria and fungi by 1·9 and 7·7% at a rate of ~3750 kg ha^-1 , and increased by 23·1 and 5·7%, at a rate of ~7500 kg ha^-1 respectively. The relative abundance of the bacteria related to soil nitrification increased, but the ones related to soil denitrification decreased with decomposed straw return, which led to higher total nitrogen contents in soils. Moreover, returning decomposed straw reduced pathogenic fungal populations (genus of Alternara), which had significantly positive correlation with soil electric conductivity. It indicated that the long-term of decomposed straw return might have lower risk of soil-borne disease mainly for the reasonable soil salinity.

CONCLUSIONS

Long-term of decomposed straw return could provide suitable nutrient and salinity for healthier development of soil microbial community, both in abundance and structure, compared with fresh straw return.

SIGNIFICANCE AND IMPACT OF THE STUDY

The results of the study helps to better understand how the microbial community modifications induced by decomposed straw return benefit on soil health. The obtained key factors impacting soil microbial community variations is meaningful in soil health management under conditions of straw return.

Effects of Pretreatment Methods of Wheat Straw on Adsorption of Cd(II) from Waterlogged Paddy Soil

Two types of pretreatment categories, namely microwave-assisted alkalization and microwave-assisted acid oxidation, were used to synthesize novel wheat straw adsorbents for the effective removal of Cd(II) in simulated waterlogged paddy soil. A systematic adsorption behavior study, including adsorption kinetics and adsorption isotherms was conducted. Results showed that wheat straw pretreated by microwave-assisted soaking of NaOH and ethanol solution obtained the highest Cd(II) removal efficiency of 96.4% at a reaction temperature of 25 ℃, pH of 7.0, initial Cd(II) concentration of 50 mg/L, and adsorbent/adsorbate ratio of 10 g/L. Sequential extraction experiment was carried out to analyze the changes of different of Cd(II) in soil, the aim of which was to study the mobility of Cd(II) and then evaluate the toxicity that Cd(II) might bring to plants. A 60-day incubation was performed to investigate the dynamic variations of soil pH and dissolved organic carbon content over incubation time. Characterization analyses revealed the morphological changes of wheat straw adsorbents, which suggested that those pretreatment methods were of significance. This study provided an environmentally friendly way to reuse agricultural wastes and remedy Cd(II) contaminated soil.

Enhanced bioremediation of 4-nonylphenol and cadmium co-contaminated sediment by composting with Phanerochaete chrysosporium inocula

Composting is identified as an effective approach for solid waste disposal. The bioremediation of 4-nonylphenol (4NP) and cadmium (Cd) co-contaminated sediment was investigated by composting with Phanerochaete chrysosporium (P. chrysosporium) inocula. P. chrysosporium inocula and proper C/N ratios (25.51) accelerated the composting process accompanied with faster total organic carbon loss, 4NP degradation and Cd passivation. Microbiological analysis demonstrated that elevated activities of lignocellulolytic enzymes and sediment enzymes was conducive to organic chemical transformation. Bacterial community diversity results illustrated that Firmicutes and Proteobacteria were predominant species during the whole composting process. Aerobic cellulolytic bacteria and organic degrading species played significant roles. Toxicity characteristic leaching procedure (TCLP) extraction and germination indices results indicated the efficient detoxification of 4NP and Cd co-contaminated sediment after 120 days of composting. Overall, results demonstrated that P. chrysosporium enhanced composting was available for the bioremediation of 4NP and Cd co-contaminated sediment.

Characterization of lignocellulosic compositions' degradation during chicken manure composting with added biochar by phospholipid fatty acid (PLFA) and correlation analysis

Biorefractory high polymer lignocellulosic compositions may limit rapid composting and stable decomposition. Because their degradation during composting is not well understood, the correlation with microbial community profiles was assessed to reveal degradation mechanism of lignocellulosic compositions. Testing of chicken manure aerobic composting with added biochar was performed using phospholipid fatty acid (PLFA) and correlation analysis. Results demonstrated a good composting effect with good dynamic correlation between microbial characteristic (PLFA) and lignocellulosic compositions' degradation ratio. The prediction model for hemicellulose degradation ratio (R²=0.97, SEP=3.24) and the prediction model for cellulose degradation ratio (R³=0.94, SEP=3.09), built using PLFA 16:0-18:2ω6c and PLFA 18:2ω6c-18:3ω3 as the arguments had good predictive ability. Based on microbial analysis and quantitative characterization of the degradation ratio, the prediction models provided methodological support for delineating the mechanism of lignocellulosic compositions' degradation during chicken manure aerobic composting with added biochar.

The impact of silver nanoparticles on the co-composting of sewage sludge and agricultural waste: Evolutions of organic matter and nitrogen

This study evaluated the influence of silver nanoparticles (AgNPs) on evolutions of organic matter and nitrogen during co-composting of sewage sludge and agricultural waste. Two co-composting piles were conducted, one was treated without AgNPs (pile 1) and the other with AgNPs (pile 2). Results showed that the AgNPs affected the quality of final composts. Less organic matter (OM) losses were determined in pile 2 (57.96%) than pile 1 (61.66%). 27.22% and 30.1% of the initial total organic matter (TOC) was decomposed in pile 1 and pile 2, respectively. The final water soluble carbon (WSC) concentration in pile 2 was 23559.27mg/kg DW compost which was significantly lower than pile 1 (25642.75mg/kg DW compost). Changes of different forms of nitrogen in the two piles showed that AgNPs could reduce the losses of TN but increase the losses of mineral N.

Microbial Biofertilizer Decreases Nicotine Content by Improving Soil Nitrogen Supply

Biofertilizers have been widely used in many countries for their benefit to soil biological and physicochemical properties. A new microbial biofertilizer containing Phanerochaete chrysosporium and Bacillus thuringiensis was prepared to decrease nicotine content in tobacco leaves by regulating soil nitrogen supply. Soil NO3--N, NH4+-N, nitrogen supply-related enzyme activities, and nitrogen accumulation in plant leaves throughout the growing period were investigated to explore the mechanism of nicotine reduction. The experimental results indicated that biofertilizer can reduce the nicotine content in tobacco leaves, with a maximum decrement of 16-18 % in mature upper leaves. In the meantime, the total nitrogen in mature lower and middle leaves increased with the application of biofertilizer, while an opposite result was observed in upper leaves. Protein concentration in leaves had similar fluctuation to that of total nitrogen in response to biofertilizer. NO3--N content and nitrate reductase activity in biofertilizer-amended soil increased by 92.3 and 42.2 %, respectively, compared to those in the control, whereas the NH4+-N and urease activity decreased by 37.8 and 29.3 %, respectively. Nitrogen uptake was improved in the early growing stage, but this phenomenon was not observed during the late growth period. Nicotine decrease is attributing to the adjustment of biofertilizer in soil nitrogen supply and its uptake in tobacco, which result in changes of nitrogen content as well as its distribution in tobacco leaves. The application of biofertilizer containing P. chrysosporium and B. thuringiensis can reduce the nicotine content and improve tobacco quality, which may provide some useful information for tobacco cultivation.

Comparison of characterization and microbial communities in rice straw- and wheat straw-based compost for Agaricus bisporus production

Rice straw (RS) is an important raw material for the preparation of Agaricus bisporus compost in China. In this study, the characterization of composting process from RS and wheat straw (WS) was compared for mushroom production. The results showed that the temperature in RS compost increased rapidly compared with WS compost, and the carbon (C)/nitrogen (N) ratio decreased quickly. The microbial changes during the Phase I and Phase II composting process were monitored using denaturing gradient gel electrophoresis (DGGE) and phospholipid fatty acid (PLFA) analysis. Bacteria were the dominant species during the process of composting and the bacterial community structure dramatically changed during heap composting according to the DGGE results. The bacterial community diversity of RS compost was abundant compared with WS compost at stages 4-5, but no distinct difference was observed after the controlled tunnel Phase II process. The total amount of PLFAs of RS compost, as an indicator of microbial biomass, was higher than that of WS. Clustering by DGGE and principal component analysis of the PLFA compositions revealed that there were differences in both the microbial population and community structure between RS- and WS-based composts. Our data indicated that composting of RS resulted in improved degradation and assimilation of breakdown products by A. bisporus, and suggested that the RS compost was effective for sustaining A. bisporus mushroom growth as well as conventional WS compost.

Activity Variation of Phanerochaete chrysosporium under Nanosilver Exposure by Controlling of Different Sulfide Sources

Due to the particular activation and inhibition behavior of silver nanoparticles (AgNPs) on microbes at various concentrations, it’s crucial to exploit the special concentration effect in environment. Here, we studied the viability variation of Phanerochaete chrysosporium (P. chrysosporium) under exposure to citrate-coated AgNPs (Citrate-AgNPs) in the presence of different sulfide sources (an inorganic sulfide, NaHS and an organic sulfide, thioacetamide (TAA)). The results indicated that both NaHS and TAA can promote activation of P. chrysosporium by Citrate-AgNPs at a higher concentration, which was initial at toxic level. Treatment with various concentrations of Citrate-AgNPs (0–9 mg/L) demonstrated a maximum activation concentration (MAC) at 3 mg/L. With the increase in sulfide concentration, MAC transferred to higher concentration significantly, indicating the obvious “toxicity to activation” transformation at a higher concentration. Ag⁺ testing exhibited that variations in sulfide-induced Ag⁺ concentration (3−7 μg/L Ag⁺) accounted for the “toxicity to activation” transformation. In addition, the similar results were observed on antibacterial application using Escherichia coli as the model species. Based on the research results, the application of this transformation in improving antibacterial activity was proposed. Therefore, the antibacterial activity of AgNPs can be controlled, even at concentration, via adjusting for the sulfide concentration.

Ammonia-oxidizing bacterial communities and shaping factors with different Phanerochaete chrysosporium inoculation regimes during agricultural waste composting

This research was conducted to determine the effects ofPhanerochaete chrysosporiuminoculation on the ammonia-oxidizing bacterial (AOB) communities during agricultural waste composting.

Fungal community dynamics and driving factors during agricultural waste composting

This study was conducted to identify the driving factors behind fungal community dynamics during agricultural waste composting. Fungal community abundance and structure were determined by quantitative PCR and denaturing gradient gel electrophoresis analysis combined with DNA sequencing. The effects of physico-chemical parameters on fungal community abundance and structure were evaluated by least significant difference tests and redundancy analysis. The results showed that Cladosporium bruhnei, Hanseniaspora uvarum, Scytalidium thermophilum, Tilletiopsis penniseti, and Coprinopsis altramentaria were prominent during the composting process. The greatest variation in the distribution of fungal community structure was statistically explained by pile temperature and total organic carbon (TOC) (P < 0.05). A significant amount of the variation (74.6 %) was explained by these two parameters alone. Fungal community abundance was found to be significantly related to pH, while pH was significantly influenced by pile temperature and nitrate levels (P < 0.05), and these parameters were found to be the most likely to influence or be influenced by the fungal community during composting.

Carbon decomposition by inoculating Phanerochaete chrysosporium during drum composting of agricultural waste

The effect of Phanerochaete chrysosporium inoculation during drum composting of agricultural waste was performed at different composting stages. Three trials were carried out with (5:4:1) combination of vegetable waste, cattle manure, and sawdust along with 10 kg of dried leaves with a total mass of 100 kg in a 550 L rotary drum composter. Trial 1 was a control without inoculation of fungus, while trial 2 was inoculated during the initial day (0th day of composting), and trial 3 was inoculated after the thermophilic phase, i.e., on the 8th day of composting period. The inoculation of fungus increased the volatile solids reduction by 1.45-fold in trial 2 and 1.7-fold in trial 3 as compared to trial 1 without any fungal inoculation. Total Kjeldahl Nitrogen (TKN) was observed with 2.31, 2.62, and 2.59% in trials 1, 2, and 3, respectively, at the end of 20 days of composting period. Hence, it can be concluded that inoculation of white-rot fungus increased the decomposition rate of agricultural waste within shorter time in drum composting. However, inoculation after the thermophilic phase was found more effective than inoculation during initial days of composting for producing more stabilized and nutrient-rich compost.

Responses of Phanerochaete chrysosporium to toxic pollutants: physiological flux, oxidative stress, and detoxification

The white-rot fungus Phanerochaete chrysosporium has been widely used for the treatment of waste streams containing heavy metals and toxic organic pollutants. The development of fungal-based treatment technologies requires detailed knowledge of the relationship between bulk water quality and the physiological responses of fungi. A noninvasive microtest technique was used to quantify real-time changes in proton, oxygen, and cadmium ion fluxes following the exposure of P. chrysosporium to environmental toxic (2,4-dichlorophenol and cadmium). Significant changes in H(+) and O(2) flux occurred after exposure to 10 mg/L 2,4-dichlorophenol and 0.1 mM cadmium. Cd(2+) flux decreased with time. Reactive oxygen species formation and antioxidant levels increased after cadmium treatment. Superoxide dismutase activity correlated well with malondialdehyde levels (r(2) = 0.964) at low cadmium concentrations. However, this correlation diminished and malondialdehyde levels significantly increased at the highest cadmium concentration tested. Real-time microscale signatures of H(+), O(2), and Cd(2+) fluxes coupled with oxidative stress analysis can improve our understanding of the physiological responses of P. chrysosporium to toxic pollutants and provide useful information for the development of fungal-based technologies to improve the treatment of wastes cocontaminated with heavy metals and organic pollutants.

Anaerobic degradation of microcrystalline cellulose: kinetics and micro-scale structure evolution

The degradation kinetics and micro-scale structure change of microcrystalline cellulose during anaerobic biodegradation were investigated. A modified Logistic model was established to properly describe the kinetics, which showed good fitness and wide applicability for cellulose degradation. A maximum degradation rate of 0.14 g L(-1) h(-1) was achieved after cultivating for 51.5 h. This result was in good agreement with the scanning electron microscope and X-ray diffraction analysis. Channels of 400-500 nm size started to occur on the crystalline surface of cellulose at around the inflexion time. Accordingly, the crystallinity significantly decreased at this point, indicating a degradation of the crystalline structure zones by anaerobic bacteria. This study offers direct morphological evidence and quantitative analysis of the biodegradation process of cellulose, and is beneficial to a better understanding of the cellulose degradation mechanism.

Abiotic and biotic dynamics during the initial stages of high solids switchgrass degradation

An understanding of the underlying dynamics of how biotic variables drive changes in abiotic parameters in the early stages of biomass biodegradation is essential for better control of the process. Probe hybridization was used to quantitatively study the growth of bacteria, yeast and fungi for three levels of initial moisture content (60, 65 and 75% MC) over a period of 64 h. Changes in abiotic parameters were also documented. By 64 h, samples were significantly differentiated both in temporal and spatial dimension, proving that considerable changes had occurred in these initial stages. Maximum carbon (C) conversion occurred in the 75% MC reactor at a peak value of 49%, with 40% and 37% in the 65 and 60% MC reactors, respectively. Higher temperature, higher pH, higher rates of O2 consumption and CO2 evolution were also observed in the highest moisture reactor; suggesting that of the three MCs studied, 75% MC was the optimal one for the process. MC during the process also proved to be important because it greatly influenced variation in the spatial dimension, further underscoring the importance of characterizing changes with bed height. Most importantly, we were able to positively correlate the rate of substrate degradation with bacterial biomass levels and highlight the critical role of bacteria in biological decomposition.

Bioactive phenolic compounds: production and extraction by solid-state fermentation. A review

Interest in the development of bioprocesses for the production or extraction of bioactive compounds from natural sources has increased in recent years due to the potential applications of these compounds in food, chemical, and pharmaceutical industries. In this context, solid-state fermentation (SSF) has received great attention because this bioprocess has potential to successfully convert inexpensive agro-industrial residues, as well as plants, in a great variety of valuable compounds, including bioactive phenolic compounds. The aim of this review, after presenting general aspects about bioactive compounds and SSF systems, is to focus on the production and extraction of bioactive phenolic compounds from natural sources by SSF. The characteristics of SSF systems and variables that affect the product formation by this process, as well as the variety of substrates and microorganisms that can be used in SSF for the production of bioactive phenolic compounds are reviewed and discussed.

Mycelial growth and solid-state fermentation of lignocellulosic waste by white-rot fungus Phanerochaete chrysosporium under lead stress

Lignocellulosic biomass is an abundant renewable resource difficult to degrade. Its bioconversion plays important roles in carbon cycles in nature, which may be influenced by heavy metals in environment. Mycelial growth and the degradation of lignocellulosic waste by lignin-degrading fungus Phanerochaete chrysosporium under lead stress were studied. It was shown that P. chrysosporium could grow in liquid media with 400 mg L⁻¹ Pb(II), and mycelial dry weight was reduced by 54% compared to the control. Yellow mycelia in irregular short-strip shape formed in Pb-containing media, whereas the control showed ivory-white regular mycelial pellets. Two possible responses to Pb stress were: dense hyphae, and secretion from mycelia to resist Pb. During solid-state fermentation of straw, fungal colonization capability under Pb stress was positively correlated with the removal efficiency of soluble-exchangeable Pb when its content was higher than 8.2 mg kg⁻¹ dry mass. Carboxymethyl cellulase activity and cellulose degradation were inhibited at different Pb concentrations, whereas low Pb concentrations increased xylanase and ligninolytic enzyme activities and the hemicellulose and lignin degradation. Cluster analyses indicated that Pb had similar effects on the different microbial indexes related to lignin and hemicellulose degradation. The present findings will advance the understandings of lignocellulose degradation by fungi under Pb pollution, which could provide useful references for developing metal-polluted waste biotreatment technology.