Cellulose Loss Research Articles

Optimization of Microwave-Assisted Organosolv Cellulose Recovery from Olive-Tree Pruning with Three Different Solvents

Research studies for cellulose recovery from lignocellulosic materials are essential in order to propose sustainable alternatives to harness residual biomasses, solving problems caused by their abundance and inadequate use. In this study, olive-tree pruning biomass has been subjected to different pretreatments with different organosolvents (acetone, ethanol, and γ-valerolactone) with microwave radiation assistance. The effect of operating parameters has been studied, considering specific ranges of variables values according to each experimental design but, in any case, located in the ranges of 33–67% (chemical compound concentration), 130–170 °C (temperature), 5–30 min (reaction time), and 1/20–1/5 (solid/liquid ratio, s/L). Based on the R2 and R2adj values (mostly above 0.97), the experimental data were adequately adjusted to four selected response variables: post-solids cellulose and lignin content apart from removal percentages of both structural components. The optimization process resulted in post-treatment solids with meaningful cellulose yields (higher than 84.7%) and reduced lignin content (lower than 4.2%). The best results were obtained using 66.5% acetone (155 °C, 8.4 min and s/L = 1/19), involving greater material deconstruction, a high percentage of delignification (96.7%), not very significant cellulose loss (29.4%), and a post-treatment solid consisting almost exclusively of cellulose (≈99%).

Autohydrolysis of sugarcane bagasse with water reuse: Impacts on residues’ composition and enzymatic hydrolysis

This work presents a new sequential approach to the sugarcane bagasse autohydrolysis process in a way that the liquor from the previous reaction was reused in the next one, and the makeup water for the next batch was used to wash the solid fraction before being added to the liquor in the next batch. This approach was suggested first as a way of reducing the water usage in the process, and second as a way of concentrating the liquor in any interesting component, working with the possibility of losing efficiency towards the glucose production through a cellulose loss to the liquor or enzymatic efficiency loss from a higher inhibitor concentration. Two sets of five sequential batches were performed: one washing the solids with the makeup water prior to the enzymatic step (Set 2), and the other one without the washing step (Set 1), looking forward to the effects of the water reuse over the glucose production and the liquor composition. Autohydrolysis pretreatment removed most of the hemicellulose (∼94 %), with liquor recycling improving its removal until the third batch and stabilizing after that. Although the washing step showed little impact on the composition of the solids, it was determinant to the success of the enzymatic hydrolysis, since it was possible to maintain the cellulose to glucose yield around 53% throughout the batches. There was a 64 % reduction in the water used in the sequential reactions without interfering in the glucose production, which indicates that the proposed strategy could be successfully used to reduce costs and environmental impacts associated with the pretreatment of lignocellulosic biomass.

Sustainable upcycling of sugarcane bagasse into nanofibrillated cellulose utilizing novel green solvents and high intensity ultrasonication

Nanofibrillated cellulose (NFC) are versatile materials with applications spanning from advanced composites to water treatment innovations. Production of NFC using biopolymers found in agricultural waste residues holds importance due to their environmentally friendly nature, providing viable substitute for non-renewable petroleum resources. From the perspective of sustainable economy, this article focuses on utilizing agricultural waste, sugarcane bagasse (SCB) for the production of nanofibrillated cellulose using green approach. Here, we synthesized four different types of acidic natural deep eutectic solvents (NADES) and investigated their potential as pretreatment agents synergistically with acetosolv, aiming to enhance cellulose recovery from SCB. The pretreatment step led to significant yield of cellulose (84.4 %) using Gly-CA NADES and acetosolv combination. The yields in case of Xyl-CA (82.2 %), Gly-TA (75.6 %) and Xyl-TA (68.9 %) were relatively lower. Subsequent implementation of high-intensity ultrasonication (HIU) process resulted in rapid nanofibrillation of fibres with minimal cellulose loss. The morphological and particle size analyses of the produced NFC samples using SEM, TEM and DLS revealed that they exhibited heterogeneity with lengths varying from 25 to 80 nm and widths varying from 5 to 10 nm, indicating a high efficiency of disintegration. The qualitative analysis of NFCs was also investigated by employing XRD, FTIR and TGA/DTG that further determined that the structure of NFCs remained unaltered even after subjecting it to various treatment methods. Thus, the study signifies a holistic approach to resource recovery and promoting sustainable and environmentally friendly biomass conversion processes.

Comparison of the transformation of organic matter flux through a raised bog and a blanket bog

AbstractThis study has proposed that organic matter transfer and transformation into and through a peatland is dominated by preferential loss of carbohydrates and the retention of lignin-like molecules. Here we used elemental analysis and thermogravimetric analysis to analyse the biomass, litter, peat soil profile, particulate organic matter, and dissolved organic matter fluxes sampled from a continental raised bog in comparison a maritime blanket bog. The macromolecular composition and thermodynamic analysis showed that in the raised bog there had been little or no transformation of the organic matter and the accumulation was rapid with comparatively little transformation with only 13% loss of cellulose by 1 m depth compared to 92% removal of cellulosic material in the blanket bog. The lack of transformation is reflected in a difference in long term carbon accumulation rates between raised and blanket bog sites. We propose that raised bogs, with their lack of a stream outfall, have high stable water tables that mean the pore water become thermodynamically closed and reactions cease higher in the peat profile than in a blanket bog where sloping sites mean a frequent flushing of pore water and discharge of water leading to fluctuating water tables, flushing of reaction products and pore spaces remaining open.

Functional conservation and preservation of waterlogged archaeological wood

Waterlogged archaeological wood of shipwrecks has been preserved under seawater for centuries, such that microbial erosion has caused severe bacterial degradation and acidification. These wooden cultural relics are of great significance for understanding the shipbuilding technology, trade activities, and environmental ecology of centuries ago. From the perspective of structure and composition, these waterlogged archeological woods have the characteristics of high water content and a large loss of lignin and cellulose, which makes the hull prone to collapse during preservation. Therefore, it is urgent to apply conservation and preservation treatments for deacidification and consolidation. Due to the fragility of wood and the complexity of repair work, the current development of conservation and preservation technology has multiple aims, such as antibacterial, deacidification, and reinforcement effects. In this editorial, the current challenges and conservation treatments with antimicrobial or deacidification utilities will be introduced.

Increasing packaging grade kraft pulp yield by using sodium methyl mercaptide

The objective of this work was to determine the effect of sodium methyl mercaptide (SMM) on the yield of the packaging-grade kraft pulp. Based on our experience with bleachable grade kraft pulping using SMM, only a co-addition of 4.38% SMM with white liquor was studied. The cooking temperature and H-factor were adjusted to reach the target kappa number. The experimental results showed about a 2.7% (on O.D. (oven dry) wood basis) increase in the pulp yield after the co-addition of 4.38% SMM (on O.D. wood basis). The use of 4.38% SMM allowed lowering of the severity of the following process variables: the white liquor effective alkali charge (EA, on O.D. wood basis) by 2.4%, the cooking temperature from 165 °C to 157 0C, and the H-factor from 535 to 295. For 98 kappa pulp, the increase in pulp yield was mostly due to the increased retention of xylan (1.63%, on wood basis) and lignin (1.71%). The retention of galactoglucomannan was negligible (0.26%). There was a minor loss of cellulose (0.70%). The increase in the pulp yield in the presence of SMM can be explained by two non-exclusive mechanisms: stabilization of carbohydrate-reducing end groups during impregnation, and faster delignification during the bulk cooking phase. Based on the experimental data, we presently do not know which of the two mechanisms for increasing the pulp yield is dominating.

Effect of ozone pretreatment of flax fiber processing waste under less water environment: Physicochemical property evaluation and digestibility metrics

Compared with the commonly used pretreatment such as organosolv, diluted acid/alkali, etc., gas phase pretreatment got the advantages of low water consumption, low reaction temperature/ time, and could degraded cellulose to smaller chains without much cellulose loss. Thus, this study pretreated flax fiber manufacturing processing waste (FFPW) with gas phase ozone for producing fermentable sugar. Experimental results showed that FFPW got about 32.5% lower lignin (13.0%) and 59.0% higher cellulose/hemicellulose ratio (3.66) compared with most of the commonly used lignocellulose materials; which make it suitable for fermentable sugar production. Gas phase pretreatment got 31.9% higher delignification rate than that under liquid phase. Under the optimal reaction condition (extra water content 79.7%, pH 3.2, ozone feed speed 101.4 mg/L/min, 21.8 min, room temperature), the FFPW get lignin content of 3.6%, cellulose content of 73.8%, digestibility of 96.1% (solid concentration 0.02 g/mL). Under high solid concentration hydrolysis (solid concentration 0.4 g/mL), ozone pretreated FFPW released 168.0 g/L glucose, which was about 10.0% higher than that of the commonly used lignocellulose materials.

A biorefinery model for the production of oil and biomethane using castor plants

AbstractCastor (Ricinus communis L.) is an important oilseed crop worldwide whose inedible oil is widely used in the industrial, pharmaceutical, and agricultural sectors. Castor plants show high conversion potential for use as biorefining feedstocks. The present study was conducted to investigate the effects of two nitrogen fertilization levels (0 and 120 kg N ha−1) on seed and oil yield. From a biorefinery perspective, the residual biomass of seed processing was analyzed in terms of fiber composition and biomethane production carrying out a biological pretreatment using two white‐rot fungi (Pleurotus ostreatus and Irpex lacteus). Nitrogen fertilization resulted in an increase in seed and oil yields and a difference in capsule husk composition. Fungal pretreatment of capsule husks showed promising effects on anaerobic digestion, increasing the biomethane yield compared to untreated biomass. The highest lignin degradation and the lowest cellulose loss during pretreatment were obtained with I. lacteus, and this fungal pretreatment resulted in the highest biomethane yield (103.2 NmL g−1 volatile solids) for the fertilized biomass.

Phosphorus-Containing Catalyst Impact on Furfural and Glucose Production during Consecutive Hydrothermal Pretreatment and Enzymatic Hydrolysis

Lignocellulosic biomasses have a very important role as raw materials to produce biobased chemicals. However, a sustainable, efficient, and economically competitive way to convert lignocellulosic biomass into these chemicals has still not been achieved. This study is related to the selective separation and conversion of birch wood C5 carbohydrates into furfural during the H3PO4–NaH2PO4-catalyzed hydrothermal pretreatment simultaneously preserving cellulose in the lignocellulosic leftover for glucose production by the enzymatic hydrolysis. The ratio of H3PO4–NaH2PO4 in the catalyst solution was changed (3:0, 2:1, 1:1, and 1:2). Results show that around 64.1 to 75.9% of available C5 carbohydrates were converted into furfural. The results of birch wood lignocellulosic leftover chemical composition analysis show that cellulose losses during the pretreatment stage did not reach more than 10% of the initial amount. Based on the enzymatic hydrolysis screening experiments, a suitable catalyst for pretreatment was selected and an in-depth study was carried out. Enzymatic hydrolysis experiments were organized based on the three-factor central composite face-centered design. The variable parameters were treatment time (24–72 h), enzyme load (10–20 U/g cellulose), and substrate amount in reaction media (10–20%). At optimal conditions, 49.9 ± 0.5% of available cellulose in lignocellulosic leftover was converted into glucose.

Establishment of patterns in the thermal modification of dry pine wood

One of the methods of ensuring the durability of dry wood during operation is its thermal modification, which inhibits the life processes of the fungus of the Ceratostomaceae family and leads to a change in its structure and properties. Therefore, the object of research was thermally modified dry pine wood affected by a fungus of the Ceratostomaceae family. Physicochemical studies of changes in the structure of thermally modified dry pine wood showed that the samples have absorption spectra that are characterized by fluctuations of the glucopyranose ring of cellulose and are an indicator of the beginning of destructive processes. At the same time, the data of thermogravimetric analysis show the processes of water loss and decomposition of hemicellulose, cellulose, and lignin, and burning of coke residue. Bending and compressive strength of thermally modified dry pine wood shows that as the wood dries, the strength limit decreases depending on the degree of fungus damage. Namely, with an area of biological damage within 10 %, the strength limit is reduced by more than 1.2 times when modified at 200 °С/3 hours, by more than 1.9 times at 200 °С/6 hours. With an increase in the degree of fungal damage to 30÷50 %, the strength limit decreases by more than 1.6 times when modified at 200 °С/3 hours, by more than 2.1 at 200 °С/6 hours. And when affected by a fungus in the range of 80÷100 %, the wood becomes softer, more plastic, while the bending strength is reduced by 1.7 times, and the compressive strength by 1.16 times. Thermal modification of dry pine wood at 200 °С for 3 hours reduces the level of water absorption by more than 1.5 times, and for 6 hours ‒ by more than 1.7 times. The practical importance is that the results of determining changes in the structure and properties of thermally modified dry pine wood make it possible to establish the scope and conditions of its application

Hot-Water Extraction (HWE) Method as Applied to Lignocellulosic Materials from Hemp Stalk

The article describes the process of hot water extraction treatment of a specific material—in this case, shavings of hemp shives of different thicknesses, sorted by their thickness into three different fractions of 0–4 mm, 4–8 mm, and 8–12 mm. In addition, each sample from a given fraction was separately subjected to one, two, and three extraction processes. After the material was treated with extraction, cellulose determination was performed using the Kürschner–Hoffer method in order to find out the effect that hot water extraction had on the cellulose content of the test material. This research aims to determine whether hot water extraction strongly alters the cellulose content, which may translate into a change in efficiency when producing second-generation biofuel produced from this material. The cellulose determination showed the smallest cellulose losses were in chips 4–8 mm thick, while the largest were in chips 0–4 mm thick. Each repetition resulted in a loss of cellulose, with the steepest loss occurring after the second repetition of HWE, and the smallest after the third repetition—the exception being the 4–8 fraction, in which the smallest decrease occurred after the first repetition of the HWE (Hot Water Extraction) process.

Preparation and Characterization of the Composition of Volatile Compounds, Fatty Acids and Thermal Behavior of Paprika.

This study aimed to investigate the thermal behavior and composition of volatile compounds, fatty acids and polyphenols in paprika obtained from peppers of different countries. The thermal analysis revealed various transformations in the paprika composition, namely drying, water loss and decomposition of volatile compounds, fatty acids, amino acids, cellulose, hemicellulose and lignin. The main fatty acids found in all paprika oils were linoleic (20.3-64.8%), palmitic (10.6-16.0%) and oleic acid (10.4-18.1%). A notable amount of omega-3 was found in spicy paprika powder varieties. The volatile compounds were classified into six odor classes (citrus (29%), woody (28%), green (18%), fruity (11%), gasoline (10%) and floral (4%)). The total polyphenol content ranged between 5.11 and 10.9 g GA/kg.

Genome sequencing and analysis of Xylaria sp. L1 provides novel insights into its utilization in IDF decomposition in okara

This study investigated the genome ofXylaria sp. L1 and its application in assisting the degradation of okara, which is an agricultural waste. The fungus process showed that there was a 50.31% cellulose loss and 56.25% hemicellulose loss, respectively. In merely 7 days, compared with untreated control, the content of insoluble dietary fiber (IDF) in the substrate was significantly decreased by 62% whereas that of soluble dietary fiber (SDF) significantly increased by 413%. Importantly, the activity of cellulase showed a continuous increase trend and it reached the maximum activity at 11.37U/g on the 7th day. The pretreated biomass showed much higher levels of polysaccharides, especially for glucuronic acid (63.63%), than the untreated controls after 7 days. Additionally, Xylaria sp. L1 sporocarps had higher quantities of macronutrients, especially for Zn. Furthermore, we conducted the first annotation of Xylaria sp. L1 genome. Illumina and nanopore sequencing revealed that the genome size of Xylaria sp. L1 was 36.61 Mb. The high activity of cellulase was in accordance with the annotation the Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), Eukaryotic Orthologous Groups (KOG), and carbohydrate-active enzymes (CAZy) databases, which are related to cellulose and hemicellulose degradation. GHs were the most abundant enzymes and 203 genes were annotated to GHs. Cellulose and hemicellulose decomposition was likely performed by an expressed GH43 and GH5 protein families containing their binding domains and genes A0779, A0819, A7717 played an important role in pentose and glucuronate interconversions. Therefore, the higher IDF decomposition by Xylaria sp. L1 makes it a prospective feedstock for okara degradation.

Reactive behaviors and mechanisms of cellulose in chemical looping combustions with iron-based oxygen carriers: An experimental combined with ReaxFF MD study

Biomass energy is one of the important and feasible renewable energy resources. Chemical looping combustion (CLC) can meet the requirements of efficient CO2 capture with low energy consumption. The combination of the two factors is intuitive and important for realizing carbon neutral energy processing and conversion. Cellulose is the component with the highest content in biomass. However, there is still a lack of clear understanding of the thermal conversion behavior and microscopic reaction mechanism of cellulose in CLC. In this work, the behaviors and mechanisms of cellulose in CLC with iron-based OCs were studied systematically based on the comprehensive technics of thermo-gravimetric analysis (TGA) experiments, kinetic models and molecular dynamic simulations. The reaction behaviors, kinetic mechanism, and complex reactive networks of cellulose under complex environmental interface conditions of CLC were revealed. Three different stages were revealed for thermal weight loss and reaction behavior of cellulose in CLC via TGA. The effects of different conversion rates and reaction stages on activation energy during CLC were described based on two model-free integration methods. The dynamic evolution of the CLC process was discussed by ReaxFF MD (reactive force field molecular dynamics) simulations. A complex reaction network of cellulose depolymerization and CO2 release in CLC was obtained.

Characterization of Lignin Peroxidase from Cryptococcus neoformans for Bioremediation of Pulp and Paper Mill Effluent

Eight fungal strains (F1–F8) isolate from the sediment core and degraded wood of the Pulp and Paper Mill effluent and Phanerochaete chrysosporium are tested for different cellulolytic (CMcase, FPase, Xylanases) and lignolytic (lignin peroxidase) enzyme activity in pulp. F-3 (Cryptococcus neoformans) strain shows higher enzyme activity compare to other fungi isolated from effluent. Weight loss, cellulose loss, and organic carbon contents are found maximum in F-3 (C. neoformans) strain. Reducing sugar, protein content, and color removing potential are also higher in C. neoformans. The culture extract of F-3 strain grows in presence of pulp fractionated into five protein fractions has indicated two fractions of molecular weight, 38,000 and 40,000 Da, having lignin peroxidase activity. Lignin peroxidase has optimum activity at pH 2–3 and temperature 20–30 °C, maximum activity at 6–48 mM veratryl alcohol concentration and 256 mM H2O2, however, sodium azide inhibits the enzyme activity. Different metals (CoCl2, HgSO4, CaCl2, SnCl2, FeSO4, CuSO4, and ZnSO4) also affect the lignin peroxidase activity. Characterization study is performed for significant analysis.

The influence of torrefaction temperature and reaction time on the properties of torrefied sun‐dried millet and sorghum straws from the arid and semi‐arid zones of western Africa

AbstractThere are increasing demands for syngas production. Fossil‐based fuels are expensive and environmentally unfriendly. Affordable, sustainable, and environmentally healthy alternatives and sustainable fuel sources are needed. This study focused on producing tor‐chars from two different tropical biomasses (from Nigeria, West Africa), which were torrefied and characterized to improve their properties for potential use as sustainable feedstocks in an entrained flow gasifier for syngas production. Torrefaction temperatures of 230, 240, 250, and 270 °C and residence times of 30 and 60 min were used to torrefy sundried sorghum straw (SS) and millet straw (MS) at particle size ≤5 mm. The properties of torrefied MS and SS improved significantly due to torrefaction. The optimum conditions for pretreatment of sundried MS and SS were 240 °C and 60 min, at which increased energy density significantly compensated for the severe mass loss and significant degradation of hemicellulose and cellulose. Under these conditions, the respective mass and energy yields were 53 wt% and 75% for millet straw and 49 wt% and 75% for sorghum straw. The O:C atomic ratio decreased to 0.3 in MS tor‐chars and 0.2 in SS tor‐chars resulting in higher heating values of 25 MJ kg−1 and 27 MJ kg−1, respectively. Under optimum conditions, the ash content increased by 107% to be approximately 7 wt% in MS tor‐char, and by 118% to about 7 wt% in SS tor‐char. These properties are promising for potential feedstocks in co‐firing plants or gasification systems. © 2022 The Authors. Biofuels, Bioproducts and Biorefining published by Society of Industrial Chemistry and John Wiley & Sons Ltd.

Optimization of Solid-State Fermentation of Switchgrass Using White-Rot Fungi for Biofuel Production

Biological delignification using white-rot fungi is a possible approach in the pretreatment of lignocellulosic biomass. Despite the considerable promise of this low-input, environmentally-friendly pretreatment strategy, its large-scale application is still limited. Therefore, understanding the best combination of factors which affect biological pretreatment and its impact on enzymatic hydrolysis is essential for its commercialization. The present study was conducted to evaluate the impact of fungal pretreatment on the enzymatic digestibility of switchgrass under solid-state fermentation (SSF) using Phanerochaete chrysosporium (PC), Trametes versicolor 52J (Tv 52J), and a mutant strain of Trametes versicolor that is cellobiose dehydrogenase-deficient (Tv m4D). Response surface methodology and analysis of variance (ANOVA) were employed to ascertain the optimum pretreatment conditions and the effects of pretreatment factors on delignification, cellulose loss, and total available carbohydrate (TAC). Pretreatment with Tv m4D gave the highest TAC (73.4%), while the highest delignification (23.6%) was observed in the PC-treated sample. Fermentation temperature significantly affected the response variables for the wild-type fungal strains, while fermentation time was the main significant factor for Tv m4D. The result of enzymatic hydrolysis with fungus-treated switchgrass at optimum pretreatment conditions showed that pretreatment with the white-rot fungi enhanced enzymatic digestibility with wild-type T. versicolor (52J)-treated switchgrass, yielding approximately 64.9% and 74% more total reducing sugar before and after densification, respectively, than the untreated switchgrass sample. Pretreatment using PC and Tv 52J at low severity positively contributed to enzymatic digestibility but resulted in switchgrass pellets with low unit density and tensile strength compared to the pellets from the untreated switchgrass.

Efficient separation of cellulose from bamboo by organic alkali

This study focuses on the effective separation of cellulose from bamboo through a two-step process. Several organic alkalies 2-pyrrolidinone, ethylurea, dibutylamine, N-methylformamide and tetramethyl guanidine were used to remove lignin and isolate cellulose from massive bamboo. The results showed that tetramethyl guanidine can effectively remove lignin and hemicellulose while retaining almost all the cellulose in the residual solid. The removal of lignin and hemicellulose achieved 86.0 and 84.0% after heating for 3 h at 150 °C, respectively. Subsequently, the final removal of lignin and hemicellulose increased to 91.5 and 93.8%, respectively, after a simple alkaline H2O2 bleach treatment. Interestingly, the loss of cellulose was very small after two-step treatments, and 96.9% of the component was still retained. The crystallinity increased from 69.8–75.2% in X-ray diffraction graphs due to the removal of lignin and hemicellulose. The Scanning electron microscopy images indicated that the diameter of cellulose bundles decreased from 80–100 µm to about 50 µm after organic alkali treatment, and then the fiber bundle was completely separated into a single long fiber with a diameter of about 10 µm after H2O2 bleaching. The Fourier transform infrared spectroscopy spectra confirmed the high selective removal of lignin and hemicellulose. Two-dimensional 1H-13 C Heteronuclear singular quantum correlation were analyzed to investigate the lignin structure and found that only the signals of –OCH3, Cγ–Hγ in β-O-4’ (Aγ) and β-β’ (Cγ) structures and C5-H5 in guaiacyl (G5) did not disappear after two-step treatment.

Species evenness affects algae driven co-metabolism with aquatic plant residues

Understanding the mixed decomposition processes of aquatic plant residues is crucial for evaluating the carbon cycle of lakes. However, the complex effect of species evenness, and especially the algae driving co-metabolism effect in eutrophic lakes are still far from clear. In this study, three dominant aquatic plants (Phragmites australis, Nymphoides peltatum, and Potamogeton malaianus) and algae from the typical eutrophic and shallow Lake Taihu, China, were selected to simulate their mixed decomposition process. The addition of algae accelerated the mass loss of cellulose, hemicellulose, and lignin of aquatic plant residues and increased the total mass loss by 2.29~6.32% in mixed decomposition. The positive co-metabolism effect, with the intensity ranging from 10% to 17%, occurred during the mixed decomposition process. In addition, the positive co-metabolism effect was also found among plant residues during mixed decomposition and the co-metabolism intensity of species evenness mixed decomposition was more than twice as high as that of non-evenness mixed decomposition. The addition of algae during the decomposition of aquatic plant residues altered the stoichiometry of available nutrients and affected the microbial decomposition activity. The abundance of decomposition bacteria, especially Bacteroidetes, was increased and the community structure also changed, as evidenced by a 71% increase in the number of bacteria phylum. As a result, these biogeochemistry processes accelerated the decomposition rates of aquatic plant residues and thus produced the positive co-metabolism effect. Therefore, the co-metabolism effects of mixed decomposition described in this study are prevalent in eutrophication lakes and have important effects on the lake carbon cycle, which need to be considered in future lake management.Graphical

Physicochemical and ultrastructural changes in fungal treated switchgrass and their impact on enzymatic digestibility

Solid-state fermentation of switchgrass using white-rot basidiomycete fungi including wild-type Trametes versicolor strain 52J (Tv 52J), a cellobiose dehydrogenase-deficient strain (mutant) T. versicolor strain m4D (Tv m4D), and wild-type Phanerochaete chrysosporium (PC) was conducted at a temperature of 34 °C, time of 28 d, hammer mill screen size of 6.4 mm and inoculum volume of 10 mL. Pretreatment with PC resulted in a significant cellulose loss (13.5 %) and slightly higher delignification compared to the other fungal strains. XRD analysis showed that fungal pretreatment increased the crystallinity index of switchgrass with PC-treated sample having 5.6 % more than untreated sample. Pretreatment resulted in approximately 5-fold and 7.7-fold increase in surface area and volume of pores, respectively, in Tvm4D-treated samples as compared to the control. SEM and TEM images revealed a significant change in cell wall morphology upon pretreatment with all three fungal strains. Fungal pretreatment of switchgrass enhanced the output of enzymatic hydrolysis.