Lignocellulosic Agricultural Residues Research Articles

Biocalorimetry-aided monitoring of fungal pretreatment of lignocellulosic agricultural residues

The present study aimed to investigate whether and how non-invasive biocalorimetric measurements could serve for process monitoring of fungal pretreatment during solid-state fermentation (SSF) of lignocellulosic agricultural residues such as wheat straw. Seven filamentous fungi representing different lignocellulose decay types were employed. Water-soluble sugars being immediately available after fungal pretreatment and those becoming water-extractable after enzymatic digestion of pretreated wheat straw with hydrolysing (hemi)cellulases were considered to constitute the total bioaccessible sugar fraction. The latter was used to indicate the success of pretreatments and linked to corresponding species-specific metabolic heat yield coefficients (YQ/X) derived from metabolic heat flux measurements during fungal wheat straw colonisation. An YQ/X range of about 120 to 140 kJ/g was seemingly optimal for pretreatment upon consideration of all investigated fungi and application of a non-linear Gaussian fitting model. Upon exclusion from analysis of the brown-rot basidiomycete Gloeophyllum trabeum, which differs from all other here investigated fungi in employing extracellular Fenton chemistry for lignocellulose decomposition, a linear relationship where amounts of total bioaccessible sugars were suggested to increase with increasing YQ/X values was obtained. It remains to be elucidated whether an YQ/X range being optimal for fungal pretreatment could firmly be established, or if the sugar accessibility for post-treatment generally increases with increasing YQ/X values as long as “conventional” enzymatic, i.e. (hemi)cellulase-based, lignocellulose decomposition mechanisms are operative. In any case, metabolic heat measurement–derived parameters such as YQ/X values may become very valuable tools supporting the assessment of the suitability of different fungal species for pretreatment of lignocellulosic substrates.Key points• Biocalorimetry was used to monitor wheat straw pretreatment with seven filamentous fungi.• Metabolic heat yield coefficients (YQ/X) seem to indicate pretreatment success.• YQ/X values may support the selection of suitable fungal strains for pretreatment.

Isolation and Characterization of a Low-Temperature, Cellulose-Degrading Microbial Consortium from Northeastern China.

The lack of efficient ways to dispose of lignocellulosic agricultural residues is a serious environmental issue. Low temperatures greatly impact the ability of organisms to degrade these wastes and convert them into nutrients. Here, we report the isolation and genomic characterization of a microbial consortium capable of degrading corn straw at low temperatures. The microorganisms isolated showed fast cellulose-degrading capabilities, as confirmed by scanning electron microscopy and the weight loss in corn straw. Bacteria in the consortium behaved as three diverse and functionally distinct populations, while fungi behaved as a single population in both diversity and functions overtime. The bacterial genus Pseudomonas and the fungal genus Thermoascus had prominent roles in the microbial consortium, showing significant lignocellulose waste-degrading functions. Bacteria and fungi present in the consortium contained high relative abundance of genes for membrane components, with amino acid breakdown and carbohydrate degradation being the most important metabolic pathways for bacteria, while fungi contained more genes involved in energy use, carbohydrate degradation, lipid and fatty acid decomposition, and biosynthesis.

Characterization of mannanases from Clonostachys byssicola involved in the breakdown of lignocellulosic substrates

Enzymatic saccharification of lignocellulosic agricultural residues, such as soybean hull, is increasingly used in Brazil to obtain fermentable sugars for use in biotechnological processes. The filamentous fungus, Clonostachys byssicola, is known to secrete an arsenal of holocellulolytic enzymes, including mannanases, which degrade the hemicellulosic components in soyabean hull. In this study, we investigated the biochemical characteristics of mannanases produced by C. byssicola. The mannanases in the concentrated crude extract (CCE) of C. byssicola showed high activity at acidic pH (5.0) and 55 °C. Furthermore, these enzymes do not depend on additional metal cofactors for their activation, although phenolic compounds inhibited the mannanase activity. Multiple forms of mannanases were identified in the CCE, which holds significance in the production of manno-oligosaccharides from different carbon sources. Scanning electron microscopy revealed structural modifications in lignocellulosic residues, including soybean hull and sugarcane bagasse, upon incubation with CCE. HPLC analysis detected mannotriose as the main oligosaccharide generated during the degradation of lignocellulosic residues. In contrast, hydrolysis of galactomannans (locust bean gum and guar gum) generated oligosaccharides of different sizes, such as mannobiose, mannotriose, mannotetraose, mannopentaose, and mannohexaose. These results highlight the potential of C. byssicola mannanases in hemicellulose degradation and production of prebiotic oligosaccharides.

Substrate dependent growth optimization of Pleurotus florida mushroom on inexpensive substrates

The oyster mushroom (Pleurotus florida) is one of the cultivated edible mushrooms and has certain medicinal properties as well as economic and ecological values. Every year, massive amounts of ligno-cellulosic agricultural crop residues are produced worldwide, and not all of them are properly utilized. There are many ways of managing agricultural waste, one of which is mushroom cultivation. This study was conducted to compare the influence of selected consortiums of agricultural residues on the growth of Pleurotus florida. This species was cultivated on different combinations of substrates, viz., dried bread grass (Brachiaria brizantha), soybean straw, sawdust, rice straw, wheat straw, cotton straw, and sugarcane bagasse. Parameters such as height of stipe, girth of stipe, width of pileus, biological efficiency, and moisture content of fruiting bodies were evaluated. All the experiments were performed in triplicate. The supreme combination of substrates was found to be dried bread grass (8%), soybean straw (15%), saw dust (25%), rice straw (20%), wheat straw (15%), cotton straw (10%), and sugarcane bagasse (7%). This combination has given the best yield in terms of mean fresh weight of fruiting bodies (56.5 g), height of stipe (3.86 cm), girth of stipe (18.33 mm), and width of pileus (5.60 cm). The maximum biological efficiency was obtained 75.55%.

Mechanically durable green aerogel composite based on agricultural lignocellulosic residue for organic liquids/oil sorption

Various oil spill cleanup sorbents have good hydrophobicity and oil separation efficiency, but their practical use has been limited due to the difficult and costly fabrication procedure. The research aims towards material development using the consumption of lignocellulosic agricultural residue for isolating cellulose nanofiber and its forward use to construct a 3D porous structure. A simple freeze-drying technique was used to assemble low-density porous structure. The biodegradable polylactic acid coating was used to alter the wettability from hydrophilic to hydrophobic and the maximum water contact angle value was around 120°. The prepared coated samples were testified for a series of oil/organic solvents-water mixtures. The sorption capacity was in the range of 28–70 g/g. The prepared aerogels were efficiently reused for at least 10 cycles. Developed material was used in continuous oil-water separation to remove oil from the water's surface. The cost analysis was estimated for scaleup production in the future.

Valorization of agricultural residues using Myceliophthora thermophila as a platform for production of lignocellulolytic enzymes for cellulose saccharification

The use of lignocellulosic agricultural residues is emerging as a low-cost, sustainable, and eco-friendly approach for the production of microbial enzymes and other chemicals. In this study, the production of enzymes with lignocellulolytic potential and the secretome profile of the thermophilic fungus Myceliophthora thermophila were evaluated in solid-state cultivation on agricultural residues such as rice straw, soy straw, and wheat bran. In addition, the saccharification potential of the extracts was evaluated. The analysis of enzymatic activities (peptidase, lipase, amylase, CMCase, FPase, β-glucosidase, xylanase, pectinase, and laccase) and the 66 proteins identified in the secretome reinforced the hydrolytic and oxidative properties of the enzymatic lignocellulolytic arsenal produced by M. thermophila. The extracellular extract grown on rice straw obtained after 72 h of solid-state bioprocess achieved 46% saccharification of wheat bran substrate. Furthermore, the overall performance of the wheat bran extract (24 h) indicates the relevance of the CMCase, FPase and xylanase activities in saccharification processes. These results highlight the potential of M. thermophila as a platform for the production of enzymes with biotechnological potential, especially for lignocellulose degradation and cellulose saccharification. Solid-state bioprocess allows exploring agro-industrial residues, as a matrix and source of nutrients, for the enzyme production and emphasizes the possibility of adding value to agricultural waste. Moreover, the use of M. thermophila in solid-state bioprocesses can still be widely explored and optimized as a platform to scale up the production of cheapest fungal enzymes.

Microbial conversion of lignin rich biomass hydrolysates to medium chain length polyhydroxyalkanoates (mcl-PHA) using Pseudomonas putida KT2440

As world moves toward increasing number of products being produced from renewable lignocellulosic agricultural and forest residues, the major classes of products that will shift to greener routes on priority are energy, fuels, and materials in that order. In materials segment, polyhydroxyalkanoates are an emerging class of biopolyesters with several potential industrial uses. The present work investigates medium chain length polyhydroxyalkanoates (mcl-PHA) producing capabilities of Pseudomonas putida KT2440 from a mixture of compounds produced from lignocellulosic biomass deconstruction. The hydrolysates obtained from nitric acid pretreatment of lignin rich cotton stalk (CS) and palm empty fruit bunch (EFB) were used as substrates for production of mcl-PHA. Presence of 3-hydroxydecanoate and 3-hydroxyocytanoate observed on GC-MS confirmed PHA accumulation in the cells. PHA accumulation was estimated between 20% and 35% of cell dry weight when grown on both model substrates as well as biomass hydrolysates. PHA titers obtained on hydrolysates of CS and EFB were 0.24 g/L and 0.21 g/L, respectively.

Comparative Highly Efficient Production of β-glucan by Lasiodiplodia theobromae CCT 3966 and Its Multiscale Characterization

Lasiodiplodan, a (1→6)-β-d-glucan, is an exopolysaccharide with high commercial value and many applications in food, pharmaceuticals, and cosmetics. Current industrial production of β-glucans from crops is mostly by chemical routes generating hazardous and toxic waste. Therefore, alternative sustainable and eco-friendly pathways are highly desirable. Here, we have studied the lasiodiplodan production from sugarcane bagasse (SCB), a major lignocellulosic agricultural residue, by Lasiodiplodia theobromae CCT 3966. Lasiodiplodan accumulated on SCB hydrolysate (carbon source) supplemented with soybean bran or rice bran (nitrogen source) was 16.2 [6.8 × 103 Da] and 22.0 [7.6 × 103 Da] g/L, respectively. Lasiodiplodan showed high purity, low solubility, pseudoplastic behavior and was composed of glucose units. Moreover, the exopolysaccharides were substantially amorphous with moderate thermal stability and similar degradation temperatures. To our knowledge, this is the first report on the highest production of SCB-based lasiodiplodan to date. L. theobromae, as a microbial cell factory, demonstrated the commercial potential for the sustainable production of lasiodiplodan from renewable biomass feedstock.

Acetobacter orientalis XJC-C with a high lignocellulosic biomass-degrading ability improves significantly composting efficiency of banana residues by increasing metabolic activity and functional diversity of bacterial community

Banana residues are an important energy resource after fruit harvesting. The optionally dumping and burning causes severely environmental problems. Traditional compost efficiency was limited by lignocellulosic composition of banana residues. Inoculation with cellulase-producing microbes provides an efficient strategy for improving degradation of lignocellulosic materials. In our study, a newly isolated cellulolytic bacterium Acetobacter orientalis XJC-C with a salt and high temperature resistance was identified from a marine soft coral. By contrast, the strain can biodegrade different lignocellulosic agricultural residues, especially banana straw. The highest cellulolytic and ligninolytic enzyme activities were detected during composting at 40 days. Compared with the negative and positive control groups, the lignin degradation rate reached 76.24% in the A. orientalis XJC-C group, increased by 47.08% and 21.85%, respectively. Moreover, the strain improved significantly the metabolic activity and functional diversity of bacterial community. Hence, A. orientalis XJC-C will be a promising candidate for degrading lignocellulosic agricultural residues.

Synthesis of a cleaner potassium hydroxide-activated carbon from baobab seeds hulls and investigation of adsorption mechanisms for diuron: Chemical activation as alternative route for preparation of activated carbon from baobab seeds hulls and adsorption of diuron

Lignocellulosic agricultural residues are worldwide used for the production of activated carbons with purpose of eliminate a large range of pollutants such as diuron, a very persistent herbicide found in streams. This work studies the adsorption of diuron in aqueous solution on two different activated carbons, a commercial activated carbon and a prepared one. Activated carbon has been produced from seed hulls of baobab (Andansonia digitata), as a valorization pathway for this waste. Precursors have been impregnated with potassium hydroxide and then carbonized under nitrogen flow. The porous structure of the carbon has been determined by methylen blue adsorption, iodine adsorption and nitrogen adsorption-desorption. The BET surface areas of the produced carbon was 1086 m2·g‒1 with an iodine and methylene blue values of 1854.2 mg·g−1 and 26.66 mg·g−1 respectively. Batch removal kinetics of diuron has been studied at 5, 13 and 20 ppm initial concentrations on the two activated carbons in a reconstituate solution. The results showed that adsorption of diuron can be modelled by Langmuir isotherm with a maximal adsorption capacity of 65.7 mg·g−1 for baobab carbon and 151.8 mg·g−1 for commercial activated carbon at 120 min equilibrium time. Speudo-second order reaction fits well with data collected during adsorption of diuron on carbons studied. Thus, Baobab seed hulls can be considered as good precursors for preparation of activated carbon with high specific surface area.

A Geographical Information System (GIS) based approach for assessing the spatial distribution and seasonal variation of biogas production potential from agricultural residues and municipal biowaste

Bioenergy can be produced from a wide range of feedstocks and can be utilised for production of renewable electricity, thermal energy, chemicals or transportation fuels. Anaerobic digestion technology (AD) for biogas production has an important role in achieving circular economy goals, as it may not only recover the energy contained in the biomass but also contribute to nutrient recovery and reduction of greenhouse gas emissions. The expansion of biogas production promotes the need for assessment of the technical potential of biomass, which is available for biogas production and is not in the competition with other purposes. This research work presents a Geographical Information System (GIS) based approach for the assessment of the spatial distribution of the biogas production potential by taking into consideration seasonal variation of biomass production, in order to assess the influence of biomass seasonality. The method developed in this research work is based on a combination of statistical and spatial explicit methods. The presented approach was tested in a case study of Croatia and the final results are representing the seasonal and spatial distribution of biogas potential at the spatial level of 1 km × 1 km. The results show that there is a strong need to include the influence of seasonality in assessment of biogas potential for lignocellulosic agricultural residues. The benefits are demonstrated in two examples that resulted in 12% and 40% lower storage facility capacity by using the proposed approach, compared to currently used approaches.

Biodegradation of lignocellulosic agricultural residues by a newly isolated Fictibacillus sp. YS-26 improving carbon metabolic properties and functional diversity of the rhizosphere microbial community

A new isolated cellulolytic bacterium from a soft coral was named as Fictibacillus sp YS-26 based on the morphologic and molecular characteristics. It can degrade different lignocellulosic agricultural residues by producing cellulolytic enzymes, α-amylase, protease, pectinase and xylanase. Especially, Fictibacillus sp. YS-26 exhibited the highest cellulolytic activities in the soybean meal medium. By contrast, the fermentation broth of Fictibacillus sp. YS-26 significantly enhanced utilization efficiency of carboxylic acids and polymers by soil microorganisms as well as the microbial metabolism function and community diversity in rhizosphere soil of banana plantlets. The fermentation broth also improved soil characters and increased the growth of banana plantlets. We found that soil total nitrogen and electrical conductivity had a positive relationship with the increase of microbial diversity. Hence, Fictibacillus sp. YS-26 will be a promising candidate for biodegradating lignocellulosic biomass and improving the soil microbial diversity.

How Vine Shoots as Fillers Impact the Biodegradation of PHBV-Based Composites.

Vine shoots are lignocellulosic agricultural residues. In addition to being an interesting source of polyphenols, they can be used as fillers in a poly(3-hydroxybutyrate-3-hydroxyvalerate) (PHBV) matrix to decrease the overall cost and to propose an alternative to non-biodegradable fossil-based materials. The objective of the present work was to investigate how the incorporation of vine shoots fillers and a preliminary polyphenol extraction step could impact the biodegradability of biocomposites. Biocomposites (20 wt %) were produced by microcompounding. The biodegradation of materials was assessed by respirometric tests in soil. The negative impact of polyphenols on the biodegradability of vine shoots was confirmed. This was supported by crystallinity measurements and scanning electron microscopy (SEM) observations, which showed no difference in structure nor morphology between virgin and exhausted vine shoots particles. The incorporation of vine shoots fillers in PHBV slightly accelerated the overall biodegradation kinetics. All the biocomposites produced were considered fully biodegradable according to the French and European standard NF EN 17033, allowing the conclusion that up-cycling vine shoots for the production of lignocellulosic fillers is a promising strategy to provide biodegradable materials in natural conditions. Moreover, in a biorefinery context, polyphenol extraction from vine shoots has the advantage of improving their biodegradability.

Laccase: An Environmental Benign Pretreatment Agent for Efficient Bioconversion of Lignocellulosic Residues to Bioethanol

Abrupt urbanization and industrialization around the world resulted in elevated environmental pollution and depletion of natural energy resources. An eco-friendly and economical alternative for energy production is the need of an hour. This can be achieved by converting the waste material into energy. One such waste is lignocellulosic agricultural residues, produced in billions of tons every year all around the world, which can be converted into bioethanol. The main challenge in this bioconversion is the recalcitrant nature of lignocellulosic material. The removal of cementing material is lignin and to overcome the potential inhibitors produced during the disintegration of lignin is the challenging task for biotechnologist. This task can be achieved by a number of different methods but laccase is the most effective and eco-friendly method that can be used for effective removal of lignin along with the increase the accessibility of cellulose and bioethanol yield.

Groundnut shell / rice husk agro-waste reinforced polypropylene hybrid biocomposites

Lignocellulosic agricultural residues are unavoidably generated and are mostly disposed by burning or burying which causes significant pollution. Using these materials for value added applications can contribute to a greener environment. In this work, two such agricultural residues namely, rice husk (RH) and groundnut shell (GNS) were used without any treatment to prepare hybrid polypropylene (PP) biocomposites for green building materials. The effects of % reinforcement on the thermal insulation, sound absorption, aqueous stability, flame resistance along with mechanical properties were tested. The unique wedge shaped morphology of rice husk and its low aspect ratio played a significant role in influencing the properties of the composites. The composites possessed good tensile and flexural strength (highest value of 15.6 MPa and 37.6 MPa respectively at the 20/60/20 GNS/RH/PP ratio). Thermal conductivity of the composites varied from 0.156 to 0.270 W/mK. The maximum sound absorption coefficient was 0.48. Flame retardancy of the composites were on par with the commercially available gypsum based ceiling tiles. Water absorption of the composites was about 85% lower than that of the gypsum tiles addressing a major drawback of gypsum based ceiling tiles. The properties of the composites were comparable to several other biocomposites reported as well.

Non-airtight fermentation of sugar beet pulp with anaerobically digested dairy manure to provide acid-rich hydrolysate for mixotrophic microalgae cultivation

Non-airtight fermentation of lignocellulosic agricultural residues with animal wastes is an emerging pretreatment method to produce acid-rich substrates in two-phase anaerobic digestion. Acid-rich hydrolysate could be an excellent feedstock for cultivating microalgae, therefore, the feasibility of a two-step process combining non-airtight fermentation of sugar beet pulp with anaerobically digested dairy manure and mixotrophic microalgae species Chlorella cultivation in the hydrolysate was explored in this study. The hydrolysis and acidification process of 8-day non-airtight fermentation produced up to 8.1 g/L volatile fatty acids under mesophilic condition. Microalgal growths in diluted hydrolysates were compared with that in diluted digested dairy manure (DDM) as a control using experimental data and fitted logistic models. Chlorella grown in the 10-fold diluted DDM showed an exponential decay, while Chlorella cultured in the 3-fold diluted hydrolysate demonstrated the best performance in terms of biomass density, which reached 2.17 g/L within a short period of time.

Coupled treatment of lignocellulosic agricultural residues for augmented biomethanation

Abstract: Naturally abundant, non-edible and inexpensive lignocellulosic biomass is an appropriate substrate for biogas production through anaerobic digestion. In order to attain most of the hydrolyzable sugars, a pretreatment phase is required before subjecting the biomass to anaerobic digestion. In this regard, lignin-degrading fungi provide an environment-friendly, clean and energy efficient process as compared to physical and chemical pretreatment methods. In the present study, biological pretreatment of pearl millet and wheat straw was carried out by employing lignolytic fungus Pleurotus ostreatus to evaluate its efficiency for making these substrates easily degradable for enhanced biogas production. Characterization of untreated and pretreated biomass was performed by employing scanning electron microscopy, Fourier transform infrared spectroscopy and thermogravimetric analysis. Maximum increase of 101 and 71% in released reducing sugars was obtained after 42 days of pretreatment for wheat and pearl millet straw, respectively. Furthermore, biogas production potential of straw (wheat and pearl millet) subjected to one stage (fungal pretreatment only) and two-stage pretreatment (fungal pretreatment and bioaugmentation with chitinolytic bacterium Bacillus subtilis after 21 days) was evaluated to improve the process. Results revealed 46 and 51% increase in methane yield following two-stage pretreatment for wheat and pearl millet straw, respectively which were higher than the methane yield obtained after fungal pretreatment alone.

Effects of alkali-treated agricultural residues on nitrate removal and N2O reduction of denitrification in unsaturated soil

Lignocellulosic agricultural residues were utilized as denitrification carbon substrates to improve the purification capacity of unsaturated soil and alleviate nitrate pollution of groundwater. In this study, corncob and wheat straw were treated by calcium hydroxide to improve biodegradability and enhance denitrification potential. Calcium hydroxide treatment decreased the contents of lignin (i.e., from 16.7 wt% to 15.2 wt% in corncob and from 21.9 wt% to 20.6 wt% in wheat straw), increased potential biodegradable carbon by 4.4–5.3 times, reached complete nitrate removal 7–14 days earlier and decreased N2O/(N2O+N2) ratios by 85–99%. The results provide an insight into the application of alkali-treated agricultural residues as denitrification carbon sources to alleviate nitrate transport to groundwater and reduce potential greenhouse effect.

Lignocellulosic biofuels in India: current perspectives, potential issues and future prospects

With the transportation sector growing considerably and demand for transport fuels rising globally, this study looks at the current and future status and technical/economic potential of lignocellulosic biofuels in India in a business-as-usual (BAU), national policy on biofuel (NPB) and 2 ℃ climate stabilization scenarios. It identifies key challenges in achieving the country’s biofuel targets, and analyses their role in India’s long-term transport scenarios. In this study, we have used ANSWER MARKAL model to assess the economic potential of biofuels obtained through lignocellulosic agricultural residues. The results indicate that the current ethanol and biodiesel availability in India through the first generation biofuel route is not sufficient to meet the country’s biofuel target. On the other hand, lignocellulosic agricultural residues can produce 38 and 51 billion litres of lignocellulosic ethanol/BTL in 2020 and 2030, respectively, which would be sufficient to meet the NPB’s 20 percent blending by 2030. Apart from biofuel availability, we assess the investment requirement for second generation biofuel industry, reduction in carbon dioxide emissions and impact on rural employment in different scenarios.

Assessment of the Influence of the Temperature in the Microwave-Assisted Alkaline Delignification of Vine Shoots

The limitation of the fossil-resources has led the research to focus on the production of biomass-based fuels from lignocellulosic agricultural residues, as it is the case of the bio-ethanol. Due to the complex and heterogeneous structure of these residues, a delignification stage is usually necessary prior to a simultaneous saccharification and fermentation treatment (SSF) for the production of bio-ethanol. In a previous work, an alkaline delignification of hydrothermally pretreated vine shoots using conventional heating was carried out in order to obtain a solid residue with low lignin and hemicellulosic content, which could be further subjected to a SSF treatment. However, when this biorefinery scheme was evaluated by a Life Cycle Assessment it was observed that the energy and chemical requirements of the delignification stage needed to be reduced. Therefore, in this work the assistance of the alkaline delignification stage by microwave was studied. The treatments were carried out at different temperatures, in order to study its influence on the lignin removal. It was observed that the microwave assistance could permit the improvement of the delignification treatments not only by increasing the delignification yield but also by reducing the temperature, time and NaOH concentration used in the treatments. The strong influence of the temperature on the chemical composition, structure and crystallinity of the delignified solids was also appreciated during this study. The solid residues obtained under the most severe conditions of the microwave-assisted alkaline delignification treatment (125 °C) could be a promising solid for the employment in a SSF treatment due to its low lignin and hemicellulosic content (16.68 % and 0.01 % respectively) and its high glucan content (50.75 %), although it presented a higher crystallinity index than the hydrothermally pretreated vine shoots.