Fungal behavior and recent developments in biopulping technology.

Biological pretreatment of wood chips by fungi is a well-known approach prior to mechanical- or chemical pulp production. For this biological approach, a limited number of white-rot fungi with an ability to colonize and selectively degrade lignin are used to pretreat wood chips allowing the remaining cellulose to be processed for further applications. Biopulping is an environmentally friendly technology that can reduce the energy consumption of traditional pulping processes. Fungal pretreatment also reduces the pitch content in the wood chips and improves the pulp quality in terms of brightness, strength, and bleachability. The bleached biopulps are easier to refine compared to pulps produced by conventional methodology. In the last decades, biopulping has been scaled up with pilot trials towards industrial level, with optimization of several intermediate steps and improvement of economic feasibility. Nevertheless, fundamental knowledge on the biochemical mechanisms involved in biopulping is still lacking. Overall, biopulping technology has advanced rapidly during recent decades and pilot mill trials have been implemented. The use of fungi as pretreatment for pulp production is in line with modern circular economy strategies and can be implemented in existing production plants. In this review, we discuss some recent advances in biopulping technology, which can improve mechanical-, chemical-, and organosolv pulping processes along with their mechanisms.

Advances in microbial pretreatment for biorefining of perennial grasses.

Perennial grasses are potentially abundant sources of biomass for biorefineries, which can produce high yields with low input requirements, and many added environmental benefits. However, perennial grasses are highly recalcitrant to biodegradation and may require pretreatment before undergoing many biorefining pathways. Microbial pretreatment uses the ability of microorganisms or their enzymes to deconstruct plant biomass and enhance its biodegradability. This process can enhance the enzymatic digestibility of perennial grasses, enabling saccharification with cellulolytic enzymes to produce fermentable sugars and derived fermentation products. Similarly, microbial pretreatment can increase the methanation rate when the grasses are used to produce biogas through anaerobic digestion. Microorganisms can also increase the digestibility of the grasses to improve their quality as animal feed, enhance the properties of grass pellets, and improve biomass thermochemical conversion. Metabolites produced by fungi or bacteria during microbial pretreatment, such as ligninolytic and cellulolytic enzymes, can be further recovered as added-value products. Additionally, the action of the microorganisms can release chemicals with commercialization potential, such as hydroxycinnamic acids and oligosaccharides, from the grasses. This review explores the recent advances and remaining challenges in using microbial pretreatment for perennial grasses with the goal of obtaining added-value products through biorefining. It emphasizes recent trends in microbial pretreatment such as the use of microorganisms as part of microbial consortia or in unsterilized systems, the use and development of microorganisms and consortia capable of performing more than one biorefining step, and the use of cell-free systems based on microbial enzymes. KEY POINTS: • Microorganisms or enzymes can reduce the recalcitrance of grasses for biorefining • Microbial pretreatment effectiveness depends on the grass-microbe interaction • Microbial pretreatment can generate value added co-products to enhance feasibility.

Effect of sequential twin screw extrusion and fungal pretreatment to release soluble nutrients from soybean residue for carotenoid production.

BACKGROUND: Soybean residue (okara) is an agricultural by-product, which is rich in protein and fiber. This study evaluated a novel sequential process which combined fungal pretreatment (F) and twin screw extruder (E), to hydrolyze okara. The sequence of the pretreatment steps, and extruder at screw speeds 200 rpm (200) or 600 rpm (600), were tested. Next, soluble nutrients were extracted to create Fokara, EFokara200, EFokara600, FEokara200 and FEokara600 okara media. RESULTS: All the prepared okara media could support the growth and carotenoid production by the yeast Rhodosporidium toruloides. This suggested that okara proteins and polysaccharides were successfully hydrolyzed by extrusion and fungal pretreatment, into soluble nutrients. Rhodosporidium toruloides accumulated the highest biomass of 23.7 mg mL-1 dry cell weight (DCW), when grown on FEokara600 media. This was higher as compared to commercial YPG (yeast extract-peptone-glycerol) media (18.7 mg mL-1 DCW). However, R. toruloides accumulated the highest carotenoid production of 13.2 µg mL-1 when grown on EFokara200 media as the nutrient source. This was comparable to carotenoid production of 13.1 µg mL-1 when R. toruloides was grown on YPG media. CONCLUSION: Extrusion in combination with fungal pretreatment, is a low cost process, to hydrolyze and re-use okara, for carotenoid production. © 2018 Society of Chemical Industry.

Improvement of selective lignin degradation in fungal pretreatment of sweet sorghum bagasse using synergistic CuSO4-syringic acid supplements.

Sweet sorghum bagasse (SSB) generated in large quantities could be hydrolyzed to sugar and then fermented to green fuels. The hydrolysis of SSB polysaccharides interlocked in recalcitrant lignin network is the major problem. Pretreatment of SSB in SSF by using Coriolus versicolor with CuSO4-syringic acid supplements for effects on production of ligninocellulolytic enzymes, lignin degradation and selectivity values (SV) were studied. C. versicolor was selected based on high ligninolytic and low cellulolytic abilily. Individually, CuSO4 increased the activities of laccase (4.9 folds) and PPO (1.9 folds); syringic acid increased LiP (13 folds), AAO (2.8 folds) and laccase (5.6 folds) resulting in increased lignin degradation and SVs. Combined syringic acid (4.4 µmol g-1 SSB) and CuSO4 (4.4 µmol g-1 SSB) increased the activities of laccase, LiP, MnP, PPO and AAO by 11.2, 17.6, 2.8, 2.4 and 2.3 folds respectively due to synergistic effect, resulting in maximum lignin degradation 35.9 ± 1.3% (w w-1) (1.86 fold) and highest SV 3.07 (4.7 fold). Enzymatic hydrolysis of pretreated SSB yielded higher (∼2.2 times) fermentable sugar. Pretreated SSB was characterized by XRD, SEM, FTIR and TGA/DTG analysis to confirm results. It is possible to improve fungal pretreatment of agricultural waste by combination of supplements.

Fungal pretreatment of willow sawdust and its combination with alkaline treatment for enhancing biogas production.

In this study fungal pretreatment of willow sawdust (WSD) via the white rot fungi Leiotrametes menziesii and Abortiporus biennis was studied and the effect on fractionation of lignocellulosic biomass and biochemical methane potential (BMP), was evaluated. Scanning electron microscopy (SEM) and IR spectroscopy were used to investigate the changes in the structural characteristics of the pretreated WSD. Fungal pretreatment results revealed that A. biennis is more attractive, since it resulted in higher lignin degradation and lower holocellulose uptake. Samples of the 14th and 30th d of cultivation (i.e. the middle and the end of the pretreatment experiment) with both fungi were used for BMP tests and the effect of pretreatment duration was also evaluated. BMP increase by 31 and 43% was obtained due to the cultivation of WSD with A. biennis, for 14 and 30 d, respectively. In addition, combination of biological (after 30 d of cultivation) with alkaline (NaOH 20 g/100 gTS) pretreatment was performed, in order to assess the effect of the chemical agent on biologically pretreated WSD, in terms of lignocellulosic content and BMP. Combination of alkaline with fungal pretreatment led to high lignin degradation for both fungi, while the cellulose and hemicellulose removal efficiencies were higher for combined alkaline and L. menziesii pretreatment. The maximum BMP was observed for the combined alkaline and A. biennis pretreatment and was 12.5 and 50.1% higher than the respective alkaline and fungal pretreatment alone and 115% higher than the respective BMP of raw WSD.

Anaerobic digestion of lignocellulosic biomasses pretreated with Ceriporiopsis subvermispora.

Fungal pretreatment by Ceriporiopsis subvermispora of two forest residues (hazel and acacia branches) and two agricultural lignocellulosic residues (barley straw and sugarcane bagasse) were studied as a pretreatment to improve their subsequent anaerobic digestion for methane production. Biomass samples were grinded to 2 ranges of particle sizes (<4 or 1 mm), autoclaved, inoculated with two strains of C. subvermispora (ATCC 90467 and ATCC 96608) and incubated at 28 °C for 28 days. The effects of fungal pretreatment were assessed by analyzing the samples before and after incubations for dry solids mass, biochemical composition, bio-methane production (BMP) and availability of cellulose to hydrolysis. The production of ligninolytic enzymes MnP and/or laccase was observed with both strains during incubation on most of the samples tested. It almost doubled the hazel branches BMP per unit mass of dry solids but did not improve however the BMP of the agricultural residues and acacia branches. These observations were explained by the fact that although both strains were able to degrade 20-25% of lignin in <1 mm and <4 mm hazel branches samples, none of them was successful however to significantly degrade lignin in the other samples, except for sugarcane bagasse.

Assessment of different pre-treatment methods for the removal of limonene in citrus waste and their effect on methane potential and methane production rate.

The objective of this study was to assess the limonene removal efficiency of three pre-treatment methods when applied to citrus waste and to evaluate their effects on the biochemical methane potential and the methane production rate using batch anaerobic tests. The methods tested were based on removal (biological pretreatment by fungi) or recovery (steam distillation and ethanol extraction) of limonene. All the treatments decreased the concentration of limonene in orange peel, with average efficiencies of 22%, 44% and 100% for the biological treatment, steam distillation and ethanol extraction, respectively. By-products from limonene biodegradation by fungi exhibited an inhibitory effect also, not making interesting the biological pretreatment. The methane potential and production rate of the treated orange peel increased significantly after applying the recovery strategies, which separated and recovered simultaneously other inhibitory components of the citrus essential oil. Apart from the high recovery efficiency of the ethanol extraction process, it presented a favourable energy balance.

Microscopic Structural Changes in Paddy Straw Pretreated with Trichoderma reesei MTCC 164 and Coriolus versicolor MTCC 138.

The present study reports the pretreatment of paddy straw by Trichoderma reesei MTCC 164 and Coriolus versicolor MTCC 138 to observe the changes in chemical composition and its correlation with change of surface structure, morphology and porosity of paddy straw. Compared with untreated straw, cellulose decreased by 15.9 and 19.3 % in T. reesei MTCC 164 and C. versicolor MTCC 138 pretreated paddy straw respectively. Lignin content increased by 41.4 % in T. reesei pretreated paddy straw whereas decreased by 19.1 % in C. versicolor pretreated straw. The microscopic structural changes were examined by scanning electron microscopy under reasonable conditions. Results showed that digestibility of paddy straw are increased by treating paddy straw with both the cultures. Both surface area and pore size of treated straw were increased partially due to solubilization of silica components.

Combination of biological pretreatment with deep eutectic solvent pretreatment for enhanced enzymatic saccharification of Pinus massoniana.

Lignocellulosic biorefineries depended on effective pretreatment strategies to improve the conversion efficiency of the enzymatic hydrolysis. Here, this study coupled brown rot fungi and deep eutectic solvent (DES) to pretreat Pinus massoniana. The results showed that compared to fungal pretreatment and DES pretreatment alone, the combined ChCl-Lac/fungal pretreatments could effectively improve enzymatic saccharification of Pinus massoniana. The highest content of releasing reducing sugar reached 510.3 mg/g substrate. Environmental scanning electron micrograph (ESEM) showed that the surface structure of Pinus massoniana was almost completely torn and loose and FT-IR spectra and component analysis revealed that most of hemicellulose and lignin were selected removed and cellulose was enriched after ChCl-Lac/fungal pretreatments, which could account for the enhanced hydrolysis efficiency. The combination of biological pretreatment with DES pretreatment could be a mild and promising pretreatment approach for enzymatic saccharification of lignocellulose and had an extensive application prospect in the field of biorefinery.

Urea impregnation into fungus pretreated corn stover to perform pyrolysis for production of nitrogen-containing bio-oil and nitrogen-doped biochar.

Urea was introduced into the fungal pretreated corn stover and then the urea soaked materials were subjected to pyrolysis for the production of nitrogen-containing bio-oil and nitrogen-doped biochar. The urea soaking effectively realized the enrichment of nitrogen-containing compounds in the bio-oil and the maximal content of the nitrogen-containing compounds in bio-oils reached up to 66.32% under 4 wt% urea concentration. Among the nitrogen-containing compounds, amines were the most dominant component with the maximal content of 41.17%. The higher urea concentration is beneficial to make more nitrogen be fixed in the biochar. The nitrogen content of the biochar reached up to 12.86 wt% under 8 wt% urea concentration. Nitrogen on the biochar surface existed in the form of pyrrolic-N, pyridinic-N and graphite-N. In conclusion, urea simple soak on fungus pretreated biomass to perform pyrolysis is a promising approach to obtain high value-added nitrogen-containing chemicals and nitrogen-doped biochar with high nitrogen content.

Improving algal growth in an anaerobic digestion piggery effluent by fungal pretreatment: Process optimization, the underlying mechanism of fungal decolorization, and nitrogen removal.

Anaerobic digestion piggery effluent (ADPE) shows high chromaticity and ammonium levels, severely inhibiting algal growth. Fungal pretreatment has great potential for decolorization and nutrient removal from wastewater, which coupled with microalgal cultivation may be a reliable strategy for sustainable ADPE resource utilization. In this study, we selected and identified two locally isolated eco-friendly fungal strains for ADPE pretreatment, and fungal culture conditions were optimized for decolorization and ammonium nitrogen (NH4+-N) removal. Subsequently, the underlying mechanisms of fungal decolorization and nitrogen removal were investigated, and the feasibility of using pretreated ADPE for algal cultivation was explored. The results showed that two fungal strains were identified as Trichoderma harzianum and Trichoderma afroharzianum, respectively, presenting good growth and decolorization performance for ADPE pretreatment. The optimized culture conditions were as follows: 20% ADPE, 8 g L-1 glucose, initial pH 6, 160 rpm, 25-30 °C, and 0.15 g L-1 initial dry-weight. ADPE decolorization was mainly caused by fungal biodegradation of color-related humic substances through manganese peroxidase secretion. The removed nitrogen was completely converted into fungal biomass as nitrogen assimilated, ca. 90% of which was attributed to NH4+-N removal. The pretreated ADPE significantly improved algal growth and nutrient removal, demonstrating the feasibility of developing an eco-friendly fungi-based pretreatment technology.

Modeling the microbial pretreatment of camelina straw and switchgrass by Trametes versicolor and Phanerochaete chrysosporium via solid-state fermentation process: A growth kinetic sub-model in the context of biomass-based biorefineries.

Advancing microbial pretreatment of lignocellulose has the potential not only to reduce the carbon footprint and environmental impacts of the pretreatment processes from cradle-to-grave, but also increase biomass valorization, support agricultural growers, and boost the bioeconomy. Mathematical modeling of microbial pretreatment of lignocellulose provides insights into the metabolic activities of the microorganisms as responses to substrate and environment and provides baseline targets for the design, development, and optimization of solid-state-fermentation (SSF) bioreactors, including substrate concentrations, heat and mass transfer. In this study, the growth of Trametes versicolor 52J (TV52J), Trametes versicolor m4D (TVm4D), and Phanerochaete chrysosporium (PC) on camelina straw (CS) and switchgrass (SG) during an SSF process was examined. While TV52J illustrated the highest specific growth rate and maximum cell concentration, a mutant strain deficient in cellulose catabolism, TVm4D, performed best in terms of holocellulose preservation and delignification. The hybrid logistic-Monod equation along with holocellulose consumption and delignification models described well the growth kinetics. The oxygen uptake rate and carbon dioxide production rate were directly correlated to the fungal biomass concentration; however, a more sophisticated non-linear relationship might explain those correlations better than a linear model. This study provides an informative baseline for developing SSF systems to integrate fungal pretreatment into a large-scale, on-farm, wet-storage process for the utilization of agricultural residues as feedstocks for biofuel production.

Effects of white-rot fungal pretreatment of corn straw return on greenhouse gas emissions from the North China Plain soil.

Straw-return with fungal treatment is a potential method for reducing soil greenhouse gas emissions through carbon (C) sequestration and N2O mitigation. However, there is little information on the effects of different fungal treatments of crop straw return on soil CO2 and N2O emissions. To explore to what extent decomposed corn straw and its components controls soil CO2 and N2O emissions, we set up three sequential incubation experiments using soil collected from the North China Plain, an intensive agricultural area. Interactions between the different C contents of corn straw (CS), CS pretreated with Irpex lacteus (ICS), CS pretreated with Phanerochaete chrysosporium (PCS) and different NO3--N concentrations on the effect of soil CO2 and N2O emissions were conducted, and the kinetics of CO2 and N2O as influenced by changes in soil biochemical factors were analyzed. The effects of different lignocellulose components (lignin, cellulose, and xylan) on soil CO2 and N2O emissions were further studied. The results showed that straw pretreatment did not affect CO2 emissions. Both CO2 and N2O emissions increased when the C and N contents increased. However, applying PCS to 70% water-filled pore space soil effectively decreased the soil N2O emissions, by 41.8%-76.3% compared with adding the same level of CS. Moreover, extracellular enzyme activities related to C and N cycling were triggered, and the nosZI and nosZII abundances were significantly stimulated by the PCS application. These effects are closely related to the initial soluble C content of this treatment. Furthermore, adding xylan can significantly reduce N2O emissions. Overall, our data suggest that the environmentally beneficial effects of returning straw can be greatly enhanced by applying the straw-degrading white-rot fungi of P. chrysosporium in the North China Plain soil. Future studies are needed in the field to upscale this technology.

Effect of pretreatment with Phanerochaete chrysosporium on physicochemical properties and pyrolysis behaviors of corn stover.

Fungal pretreatment can selectively degrade partial biomass components, which undoubtedly exerts a significant influence on biomass pyrolysis behavior. The corn stover was pretreated with Phanerochaete chrysosporium, and its influence on the physicochemical properties and pyrolysis behaviors of biomass together with the product characteristics were investigated. The Phanerochaete chrysosporium was more active to degrade hemicellulose and lignin. The hemicellulose and lignin contents in corn stover were decreased by 35.14 % and 31.80 %, respectively, after five weeks pretreatment, compared to the untreated sample. The reaction activation energy decreased from 52.89 kJ·mol-1 for the untreated sample to 40.88 kJ·mol-1 for the sample pretreated for five weeks. The Phanerochaete chrysosporium pretreatment was beneficial to the biochar production but exerted an unfavorable effect on the texture structure. The Phanerochaete chrysosporium also had an obvious influence on the bio-oil compositions. This study can provide a scientific reference for the application of biological pretreatment for biomass pyrolysis technology.

Solid-State Fermentation of Chestnut Shells and Effect of Explanatory Variables in Predictive Saccharification Models.

In this study, chestnut shells (CNS), a recalcitrant and low-value agro-industrial waste obtained during the peeling of Castanea sativa fruits, were subjected to solid-state fermentation by six white-rot fungal strains (Irpex lacteus, Ganoderma resinaceum, Phlebia rufa, Bjerkandera adusta and two Trametes isolates). After being fermented, CNS was subjected to hydrolysis by a commercial enzymatic mix to evaluate the effect of fermentation in saccharification yield. After 48 h hydrolysis with 10 CMCase U mL−1 enzymatic mix, CNS fermented with both Trametes strains was recorded with higher saccharification yield (around 253 mg g−1 fermented CNS), representing 25% w/w increase in reducing sugars as compared to non-fermented controls. To clarify the relationships and general mechanisms of fungal fermentation and its impacts on substrate saccharification, the effects of some independent or explanatory variables in the production of reducing sugars were estimated by general predictive saccharification models. The variables considered were lignocellulolytic activities in fungal fermentation, CNS hydrolysis time, and concentration of enzymatic hydrolysis mix. Multiple linear regression analysis revealed a very high significant effect (p < 0.0001) of fungal laccase and xylanase activities in the saccharification models, thus proving the key potential of these enzymes in CNS solid-state fermentation.

Shiitake cultivation as biological preprocessing of lignocellulosic feedstocks - Substrate changes in crystallinity, syringyl/guaiacyl lignin and degradation-derived by-products.

Formulation of substrates based on three hardwood species combined with modulation of nitrogen content by whey addition (0-2%) was investigated in an experiment designed in D-optimal model for their effects on biological preproceesing of lignocellulosic feedstock by shiitake mushroom (Lentinula edodes) cultivation. Nitrogen loading was shown a more significant role than wood species for both mushroom production and lignocellulose degradation. The fastest mycelial colonisation occurred with no nitrogen supplementation, but the highest mushroom yields were achieved when 1% whey was added. Low nitrogen content resulted in increased delignification and minimal glucan consumption. Delignification was correlated with degradation of syringyl lignin unit, as indicated by a significant reduction (41.5%) of the syringyl-to-guaiacyl ratio after cultivation. No significant changes in substrate crystallinity were observed. The formation of furan aldehydes and aliphatic acids was negligible during the pasteurisation and fungal cultivation, while the content of soluble phenolics increased up to seven-fold.

An overview of fungal pretreatment processes for anaerobic digestion: Applications, bottlenecks and future needs.

Lignin modifying or extracellular enzymes secreted by the white rot fungi have the ability of degrading wide range of lignocellulosic substrates and organic pollutants. Lignocellulosic biomass, despite being a renewable source of energy, is difficult to hydrolyse (hydrolysis being rate-limiting stage in anaerobic digestion process). Various pre-treatment techniques like physical, chemical, thermo-chemical and biological to enhance the accessibility of microbes to carbohydrates have been studied. Recently, usage of white- rot fungi in a biological pre-treatment technique have received renewed interest due to its low cost and eco-friendly nature. This review deals with: a) lignocellulosic biomass recalcitrance, b) various pre-treatment techniques and its economic feasibility, c) delignification and hydrolysis mechanism using white-rot fungi, d) factors controlling white-rot fungi pre- treatment process, and e) improvement in methane production through solid-state anaerobic digestion of white-rot fungi pre-treated lignocellulosic biomass. Finally a future perspective is also included.

A Two-step Strategy for High-Value-Added Utilization of Rapeseed Meal by Concurrent Improvement of Phenolic Extraction and Protein Conversion for Microbial Iturin A Production.

Rapeseed meal (RSM) is a major by-product of oil extraction from rapeseed, consists mainly of proteins and phenolic compounds. The use of RSM as protein feedstock for microbial fermentation is always hampered by phenolic compounds, which have antioxidant property with health-promoting benefits but inhibit bacterial growth. However, there is still not any good process that simultaneously improve extraction efficiency of phenolic compounds with conversion efficiency of protein residue into microbial production. Here we established a two-step strategy including fungal pretreatment followed by extraction of phenolic compounds. This could not only increase extraction efficiency and antioxidant property of phenolic compounds by about 2-fold, but also improve conversion efficiency of protein residue into iturin A production by Bacillus amyloliquefaciens CX-20 by about 33%. The antioxidant and antibacterial activities of phenolic extracts were influenced by both total phenolic content and profile, while microbial feedstock value of residue was greatly improved because protein content was increased by ∼5% and phenolic content was decreased by ∼60%. Moreover, this two-step process resulted in isolating more proteins from RSM, bringing iturin A production to 1.95 g/L. In conclusion, high-value-added and graded utilization of phenolic extract and protein residue from RSM with zero waste is realized by a two-step strategy, which combines both benefits of fungal pretreatment and phenolic extraction procedures.

Improvement of solid-state anaerobic digestion of broiler farm-derived waste via fungal pretreatment.

Fungus, Trichoderma longibrachiatum, was used for the pretreatment of broiler farm derived-lignocellulosic bedding material (rice husk) to enhance the subsequent solid-state anaerobic digestion (SS-AD). Fungal pretreatment efficacy was evaluated through a series of batch studies with respect to carbon-to-nitrogen (C/N) ratio and pretreatment time. Lignocellulosic outer layer structure disruption of the rice husk was prominent under the best fungal pretreatment condition evaluated (C/N ratio of 18.9 and pretreatment time of 7 days). Consequently, the resulting methane yield of 438.1 ± 20.0 NmL/gVSadded was obtained which was ~2.0-folds higher than that of the control (without pretreatment). Furthermore, in semi-continuous SS-AD, fungal pretreatment could significantly enhance digestibility of organic substance in high solid loading (30% total solids) AD process by 3.2-folds and improve microbial kinetic parameters with subsequent daily methane yield improvement by 2.4-folds. Thus, fungal pretreatment could be an environmentally-friendly and effective low-cost approach for broiler farm-derived waste management to enhance SS-AD efficacy.

Improvement of empty palm fruit bunches biodegradability and biogas production by integrating the straw mushroom cultivation as a pretreatment in the solid-state anaerobic digestion.

Empty fruit bunches (EFB) have low biodegradability and restrict their commercial utilization in biogas plants. Integration of straw mushroom (Volvariella volvacea) cultivation as a function of bio-pretreatment on EFB to improve biodegradability and methane production by solid-state anaerobic digestion (SS-AD) was investigated. The mushroom yield was 47.3 kg·tonne-1 EFB with remaining weight in spent mushroom-EFB (S-mEFB) of 82%. The cellulose, hemicellulose, and lignin of EFB were degraded by 3.3%, 21.3%, and 17.6%, respectively, with an increased surface area of S-mEFB. The biodegradability of S-mEFB (62.7%) was 2 times higher than raw EFB (33.5%) with the highest methane yield and production of 281 mL CH4·g-1 VS and 50.6 m3·tonne-1 S-mEFB, respectively. The co-digestion of S-mEFB with 5% v/w POME had highest methane yield of 405 mL CH4·g-1 VS with biodegradability of 90.8%. Integrating straw mushroom cultivation with SS-AD is a promising strategy for achieving an environmentally friendly and economically feasible process.