Statistical Optimization of Laccase Production and Delignification of Sugarcane Bagasse by Pleurotus ostreatus in Solid-State Fermentation

Decisional tool development and application for techno-economic analysis of fungal laccase production

Textile and medical effluents causing bioaccumulation and biomagnification have been successfully biodegraded by fungal laccases. Here, a decision-making tool was developed and applied to evaluate 45 different laccase production strategies which determined the best potential source from a techno-economical perspective. Laccase production cost was calculated with a fixed output of 109 enzymatic units per batch (USD$per109U) and a sensitivity analysis was performed. Results indicate that optimization of enzymatic kinetics for each organism is essential to avoid exceeding the fermentation time point at which production titer reaches its peak and, therefore, higher production costs. Overall, the most cost-effective laccase-producing strategy was obtained when using Pseudolagarobasidium acaciicola with base production cost of USD $42.46 per 109 U. This works serves as platform for decision-making to find the optimal laccase production strategy based on techno-economic parameters.

Valorization of sugarcane bagasse for high-yield production of laccase through Aspergillus terreus for effective azo dye decolourization

Synthetic dyes such as azo dyes are significant pollutants in the wastewater released from various textile industries. The low biodegradability and production from synthetic sources with high shelf life make azo dyes a challenging material for degradation. This study used chemically mutated Aspergillus terrus in the laccase production under solid-state fermentation using sugarcane bagasse. Initially, the wild-type strain produced a laccase activity of 4.12 U/mL. Later, the alkaline pretreatment of sugarcane bagasse showed a significant increase in laccase activity by 38.9%. Further, random mutagenesis treatment with 100 mM EMS generated a hyper laccase-producing strain with a 2.3-fold increment in laccase activity compared to the wild-type strain. The enzyme displayed optimal activity at pH 6.5 and 35 °C. The metal ions such as Fe3+ (29.4 U/mL), Fe2+ (20.8 U/mL) and Cu2+ (18.05 U/mL) showed positive effects on laccase activity. The crude laccase was used to bioremediate Congo red, a prominent azo dye used in textile and pharmaceutical industries. The preliminary studies with a crude enzyme displayed 68.86% dye decolourization after 24 h of incubation. Additionally, with Taguchi orthogonal array optimization experiments, the maximal dye decolorization of 78.24% was achieved by maintaining crude enzyme concentration (20 U), dye concentration (25 mg/L) and pH 4.5.

Laccase mediated delignification of wasted and non-food agricultural biomass: Recent developments and challenges

Utilization of microbial laccases is considered as the cleaner and target specific biocatalytic mechanism for the recovery of cellulose and hemicelluloses from nonfood and wasted agricultural, lignocellulosic biomass (LCB). The extent of lignin removal by laccase depends on the biochemical composition of biomass and the redox potential (E⁰) of the biocatalyst. Intensive research efforts are going on all over the world for the recognition of appropriate and easily available agricultural lignocellulosic feedstocks to exploit maximally for the production of value-added bioproducts and biofuels. In such circumstances, laccase can play a major role as a leading biocatalyst and potent substitute for chemical based deconstruction of the lignocellulosic materials. The limited commercialization of laccase at an industrial scale has been feasible due to its full working efficiency mostly expressed in the presence of cost intensive redox mediators only. Although, recently there are some reports that came on the mediator free biocatalysis of enzyme but still not considerably explored and neither understood in depth. The present review will address the various research gaps and shortcomings that acted as the big hurdles before the complete exploitation of laccases at an industrial scale. Further, this article also reveals insights on different microbial laccases and their diverse functional environmental conditions that affect the deconstruction process of LCB.

Laccase production by Pleurotus ostreatus using cassava waste and its application in remediation of phenolic and polycyclic aromatic hydrocarbon-contaminated lignocellulosic biorefinery wastewater

The treatment of contaminants from lignocellulosic biorefinery effluent has recently been identified as a unique challenge. This study focuses on removing phenolic contaminants and polycyclic aromatic hydrocarbons (PAHs) from lignocellulosic biorefinery wastewater (BRW) applying a laccase-assisted approach. Cassava waste was used as a substrate to produce the maximum yield of laccase enzyme (3.9 U/g) from Pleurotus ostreatus. Among the different inducers supplemented, CuSO₄ (0.5 mM) showed an eight-fold increase in enzyme production (30.8 U/g) after 240 h of incubation. The catalytic efficiency of laccase was observed as 128.7 ± 8.47 S^-1mM^-1 for syringaldazine oxidation at optimum pH 4.0 and 40 °C. Laccase activity was completely inhibited by lead (II) ion, mercury (II) ion, sodium dodecyl sulphate, sodium azide and 1,4 dithiothretiol and induced significantly by manganese (II) ion and rhamnolipid. After treating BRW with laccase, the concentrations of PAHs and phenolic contaminants of 1144 μg/L and 46160 μg/L were reduced to 96 μg/L and 16100 μg/L, respectively. The ability of laccase to effectively degrade PAHs in the presence of different phenolic compounds implies that phenolic contaminants may play a role in PAHs degradation. After 240 h, organic contaminants were removed from BRW in the following order: phenol >2,4-dinitrophenol > 2-methyl-4,6-dinitrophenol > 2,3,4,6-tetrachlorophenol > acenaphthene > fluorine > phenanthrene > fluoranthene > pyrene > anthracene > chrysene > naphthalene > benzo(a)anthracene > benzo(a)pyrene > benzo(b)fluoranthene > pentachlorophenol > indeno(1,2,3-cd)pyrene > benzo(j) fluoranthene > benzo[k]fluoranthène. The multiple contaminant remediation from the BRW by enzymatic method, clearly suggests that the laccase can be used as a bioremediation tool for the treatment of wastewater from various industries.

The production of laccases by white-rot fungi under solid-state fermentation conditions

Laccases (E.C. 1.10.3.2) produced by white-rot fungi (WRF) can be widely used, but the high cost prevents their use in large-scale industrial processes. Finding a solution to the problem could involve laccase production by solid-state fermentation (SSF) simulating the natural growth conditions for WRF. SSF offers several advantages over conventional submerged fermentation (SmF), such as higher efficiency and productivity of the process and pollution reduction. The aim of this review is therefore to provide an overview of the current state of knowledge about the laccase production by WRF under SSF conditions. The focus is on variations in the up-stream process, fermentation and down-stream process and their impact on laccase activity. The variations of up-stream processing involve inoculum preparation, inoculation of the medium and formulation of the propagation and production media. According to the studies, the production process can be shortened to 5-7 days by the selection of a suitable combination of lignocellulosic material and laccase producer without the need for any additional components of the culture medium. Efficient laccase production was achieved by valorisation of wastes as agro-food, municipal wastes or waste generated from wood processing industries. This leads to a reduction of costs and an increase in competitiveness compared to other commonly used methods and/or procedures. There will be significant challenges and opportunities in the future, where SSF could become more efficient and bring the enzyme production to a higher level, especially in new biorefineries, bioreactors and biomolecular/genetic engineering.

Insights on sustainable approaches for production and applications of value added products

The increasing demand for the development of sustainable strategies to utilize and process agro-industrial residues paves new paths for exploring innovative approaches in this area. Biotechnology based microbial transformations provide efficient, low cost and sustainable approaches for the production of value added products. The use of organic rich residues opens new avenues for the production of enzymes, pigments, biofuels, bioactive compounds, biopolymers etc. with vast industrial and therapeutic applications. Innovative technologies like strain improvement, enzyme immobilization, genome editing, morphological engineering, ultrasound/supercritical fluid/pulse electric field extraction, etc. can be employed. These will be helpful in achieving significant improvement in qualitative and quantitative parameters of the finished products. The global trend for the valorisation of biowaste has boosted the commercialization of these products which has transformed the markets by providing new investment opportunities. The upstream processing of raw materials using microbes poses a limitation in terms of product development and recovery which can be overcome by modifying the bioreactor design, physiological parameters or employing alternate technologies which will be discussed in this review. The other problems related to the processes include product stability, industrial applicability and cost competitiveness which needs to be addressed. This review comprehensively discusses the recent progress, avenues and challenges in the approaches aimed at valorisation of agro-industrial wastes along with possible opportunities in the bioeconomy.

Effect of Nutritional Factors and Copper on the Regulation of Laccase Enzyme Production in Pleurotus ostreatus

This research aimed to establish the relationship between carbon–nitrogen nutritional factors and copper sulfate on laccase activity (LA) by Pleurotus ostreatus. Culture media composition was tested to choose the nitrogen source. Yeast extract (YE) was selected as a better nitrogen source than ammonium sulfate. Then, the effect of glucose and YE concentrations on biomass production and LA as response variables was evaluated using central composite experimental designs with and without copper. The results showed that the best culture medium composition was glucose 45 gL⁻¹ and YE 15 gL⁻¹, simultaneously optimizing these two response variables. The fungal transcriptome was obtained in this medium with or without copper, and the differentially expressed genes were found. The main upregulated transcripts included three laccase genes (lacc2, lacc6, and lacc10) regulated by copper, whereas the principal downregulated transcripts included a copper transporter (ctr1) and a regulator of nitrogen metabolism (nmr1). These results suggest that Ctr1, which facilitates the entry of copper into the cell, is regulated by nutrient-sufficiency conditions. Once inside, copper induces transcription of laccase genes. This finding could explain why a 10–20-fold increase in LA occurs with copper compared to cultures without copper when using the optimal concentration of YE as nitrogen sources.

A comparative study of greener alternatives for nanocellulose production from sugarcane bagasse

Use of enzyme for extraction of nanocellulose from sugarcane bagasse is greener alternative. Literature indicates that effectiveness of these enzymes can be improved by auxiliary enzymes or mediators. In the current study, extraction of nanocellulose using laccase with these moderators, auxiliary enzyme glucose oxidase and mediator molecule, ABTS [2,2'-azinobis(3-ethylbenzthiazoline-6-sulfonate)] individually was done. Cellulose and lignin content, FT-IR, TGA and DSC analysis, XRD, SEM and PSA were done. Enzyme moderators improved the performance of laccase in lignin degradation. Lignin and cellulose content, crystallinity were used as parameters to optimize the concentrations, which was found to be ABTS (at 1.4 mM) and glucose oxidase (at 0.15 mg ml-1). At the optimal concentration, nanocellulose was extracted. Properties of nanocellulose obtained from both routes were compared. Size analysis revealed 339 nm and 636 nm for nanocellulose obtained with glucose oxidase and ABTS, respectively. Defibrillation was better in the case of the former one as seen from SEM.

Recent Developments in the Immobilization of Laccase on Carbonaceous Supports for Environmental Applications - A Critical Review

Τhe ligninolytic enzyme laccase has proved its potential for environmental applications. However, there is no documented industrial application of free laccase due to low stability, poor reusability, and high costs. Immobilization has been considered as a powerful technique to enhance laccase's industrial potential. In this technology, appropriate support selection for laccase immobilization is a crucial step since the support could broadly affect the properties of the resulting catalyst system. Through the last decades, a large variety of inorganic, organic, and composite materials have been used in laccase immobilization. Among them, carbon-based materials have been explored as a support candidate for immobilization, due to their properties such as high porosity, high surface area, the existence of functional groups, and their highly aromatic structure. Carbon-based materials have also been used in culture media as supports, sources of nutrients, and inducers, for laccase production. This study aims to review the recent trends in laccase production, immobilization techniques, and essential support properties for enzyme immobilization. More specifically, this review analyzes and presents the significant benefits of carbon-based materials for their key role in laccase production and immobilization.

Isolation of Fungi from a Textile Industry Effluent and the Screening of Their Potential to Degrade Industrial Dyes

Six fungal strains were isolated from the textile industry effluent in which they naturally occur. Subsequently, the fungal strains were identified and characterized in order to establish their potential decolorizing effect on textile industry effluents. The strains of interest were selected based on their capacity to decolorize azo, indigo, and anthraquinone dyes. Three of the strains were identified as Emmia latemarginata (MAP03, MAP04, and MAP05) and the other three as Mucor circinelloides (MAP01, MAP02, and MAP06), while the efficiency of their decolorization of the dyes was determined on agar plate and in liquid fermentation. All the strains co-metabolized the dyes of interest, generating different levels of dye decolorization. Plate screening for lignin-degrading enzymes showed that the MAP03, MAP04, and MAP05 strains were positive for laccase and the MAP01, MAP02, and MAP06 strains for tyrosinase, while all strains were positive for peroxidase. Based on its decolorization capacity, the Emmia latemarginata (MAP03) strain was selected for the further characterization of its growth kinetics and ligninolytic enzyme production in submerged fermentation under both enzyme induction conditions, involving the addition of Acetyl yellow G (AYG) dye or wheat straw extract, and no-induction condition. The induction conditions promoted a clear inductive effect in all of the ligninolytic enzymes analyzed. The highest level of induced enzyme production was observed with the AYG dye fermentation, corresponding to versatile peroxidase (VP), manganese peroxidase (MnP), and lignin peroxidase (LiP). The present study can be considered the first analysis of the ligninolytic enzyme system of Emmia latemarginata in submerged fermentation under different conditions. Depending on the results of further research, the fungal strains analyzed in the present research may be candidates for further biotechnological research on the decontamination of industrial effluents.

Enrichment of laccase production by Phoma herbarum isolate KU4 under solid-state fermentation by optimizing RSM coefficients using genetic algorithm

The process parameters were optimized to obtain enhanced enzyme activity from the fungus Phoma herbarum isolate KU4 using rice straw and saw dust as substrate under solid-state fermentation using Response surface methodology (RSM). Genetic algorithm was used to validate the RSM for maximum laccase production. Six variables, viz., pH of the media, initial moisture content, copper sulphate concentration, concentration of tannic acid, inoculum concentration and incubation time were found to be effective and optimized for enhanced production. Maximum laccase production was achieved by RSM at pH 5·0 and 86% of initial moisture content of the culture medium, 150 µmol l^-1 of CuSO₄ , 1·5% tannic acid and 0·128 g inoculum g^-1 dry substrate inoculum size on the fourth day of fermentation. The highest laccase activity was observed as 79 008 U g^-1 , which is approximately sixfold enhanced production compared to the unoptimized condition (12 085·26 U g^-1 ).

Isolation, identification and optimization of enhanced production of laccase from Galactomyces geotrichum under solid-state fermentation

Laccases are a group of oxidases that catalyze the oxidation of a wide range of electron rich substrates like phenolic compounds, lignin and aromatic amines. They are of interest because of their potential to be used in environmental and industrial applications. In this research, potent laccase producer fungi were screened and isolated from olive mill wastewater (OMW). One of the 23 isolated fungi was identified as Galactomyces geotrichum based on 18S rDNA sequence analysis that detected good laccase activity. Produced laccase had a molecular weight of 55 kDa that was confirmed by zymogram analysis. This is the first report about the optimization of laccase Production by G. geotrichum under solid-state fermentation. The optimization was made by the Taguchi design of experiments (DOE) methodology. An orthogonal array (L25) was designed using Minitab 19 software to study four effective process factors in five levels for laccase production. The optimum condition derived was; moisture content (80%), fermentation time (14 day), CuSO₄⋅5H₂O as the inducer (300 μM), glucose as a co-substrate (5 g/L). Maximum laccase activity of 52.86 (U/g of dry substrate) was obtained using optimum fermentation condition. This study aimed to better understand the laccase producing microorganisms in OMW and take them to OMW treatment that is rich in phenolic compounds.

Cultivation of Mushrooms and Their Lignocellulolytic Enzyme Production Through the Utilization of Agro-Industrial Waste

A large amount of agro-industrial waste is produced worldwide in various agricultural sectors and by different food industries. The disposal and burning of this waste have created major global environmental problems. Agro-industrial waste mainly consists of cellulose, hemicellulose and lignin, all of which are collectively defined as lignocellulosic materials. This waste can serve as a suitable substrate in the solid-state fermentation process involving mushrooms. Mushrooms degrade lignocellulosic substrates through lignocellulosic enzyme production and utilize the degraded products to produce their fruiting bodies. Therefore, mushroom cultivation can be considered a prominent biotechnological process for the reduction and valorization of agro-industrial waste. Such waste is generated as a result of the eco-friendly conversion of low-value by-products into new resources that can be used to produce value-added products. Here, we have produced a brief review of the current findings through an overview of recently published literature. This overview has focused on the use of agro-industrial waste as a growth substrate for mushroom cultivation and lignocellulolytic enzyme production.

Fungal Laccase Production from Lignocellulosic Agricultural Wastes by Solid-State Fermentation: A Review

Laccases are copper-containing oxidase enzymes found in many fungi. They have received increasing research attention because of their broad substrate specificity and applicability in industrial processes, such as pulp delignification, textile bleaching, phenolic removal, and biosensors. In comparison with traditional submerged fermentation (SF), solid-state fermentation (SSF) is a simpler technique for laccase production and has many advantages, including higher productivity, efficiency, and enzyme stability as well as reduced production costs and environmental pollution. Here, we review recent advances in laccase production technology, with focus on the following areas: (i) Characteristics and advantages of lignocellulosic agricultural wastes used as SSF substrates of laccase production, including detailed suggestions for the selection of lignocellulosic agricultural wastes; (ii) Comparison of fungal laccase production from lignocellulosic substrates by either SSF or SF; (iii) Fungal performance and strain screening in laccase production from lignocellulosic agricultural wastes by SSF; (iv) Applications of laccase production under SSF; and (v) Suggestions and avenues for future studies of laccase production by fungal SSF with lignocellulosic materials and its applications.

Bioprocess optimization of laccase production through solid substrate fermentation using Perenniporia tephropora-L168 and its application in bioremediation of triaryl-methane dye

Laccases are multi copper oxidases that can oxidize both phenolic and nonphenolic lignin related compounds. Consequently, there has been continuous demand for laccases for the oxidative degradation of phenolic dyes in effluents. In view of this, the present work was focused on laccase production by solid substrate fermentation using a newly isolated fungus Perenniporia tephropora-L168. To intensify the laccase production, the process parameters pH, nitrogen, inducer, and substrate: water ratio were optimized by using statistical model. A set of optimal conditions noted were pH 3, nitrogen 0.001 g/L; inducer 0.5% and substrate: water ratio (1:10), which yielded laccase 1,160 U/g. The crude laccase exhibited noteworthy potential to degrade a triaryl-methane dye especially Malachite green. Also, during bioremediation studies, the statistical process optimization could achieve 81% decolourization within 180 min. The laccase treatment brought chemical transformation in malachite green as evident from UV-Visible spectra, FTIR, HPLC while toxicity against bacteria and fungi was also reduced. During phytotoxicity study, effect of treated and untreated dye on germination of seed was analyzed. Interestingly, the germination index for Vigna aconitifolia and Vigna radiata was increased by two and fourfold, respectively. Overall, this work demonstrates optimized production of laccase using Perenniporia tephropora-L168 and its efficient bioremediation potential for triaryl-methane dye.

Evaluation of laccase production by Ganoderma lucidum in submerged and solid-state fermentation using different inducers

Laccases are multicopper oxidases with high potential for industrial applications. Several basidiomycete fungi are natural producers of this enzyme; however, the optimization of production and selection of inducers for increased productivity coupled with low costs is necessary. Lignocellulosic residues are important lignin sources and potential inducers for laccase production. Pinus taeda, a dominant source of wood-based products, has not been investigated for this purpose yet. The aim of this study was to evaluate the production of laccase by the basidiomycete fungus Ganoderma lucidum in the presence of different inducers in submerged and solid-state fermentation. The results of submerged fermentation in presence of 5 μM CuSO ₄ , 2 mM ferulic acid, 0.1 g/L P. taeda sawdust, or 0.05 g/L Kraft lignin indicated that although all the tested inducers promoted increase in laccase activity in specific periods of time, the presence of 2 mM ferulic acid resulted in the highest value of laccase activity (49 U/L). Considering the submerged fermentation, experimental design following the Plackett-Burman method showed that the concentrations of ferulic acid and P. taeda sawdust had a significant influence on the laccase activity. The highest value of 785 U/L of laccase activity on submerged fermentation was obtained on the seventh day of cultivation. Finally, solid-state fermentation cultures in P. taeda using ferulic acid or CuSO ₄ as inducers resulted in enzymatic activities of 144.62 and 149.89 U/g, respectively, confirming the potential of this approach for laccase production by G. lucidum.

Role of the antioxidant defense system during the production of lignocellulolytic enzymes by fungi

Fungi are used for the production of several compounds and the efficiency of biotechnological processes is directly related to the metabolic activity of these microorganisms. The reactions catalyzed by lignocellulolytic enzymes are oxidative and generate reactive oxygen species (ROS). Excess of ROS can cause serious damages to cells, including cell death. Thus, the objective of this work was to evaluate the lignocellulolytic enzymes produced by Pleurotus sajor-caju CCB020, Phanerochaete chrysosporium ATCC 28326, Trichoderma reesei RUT-C30, and Aspergillus niger IZ-9 grown in sugarcane bagasse and two yeast extract (YE) concentrations and characterize the antioxidant defense system of fungal cells by the activities of superoxide dismutase (SOD) and catalase (CAT). Pleurotus sajor-caju exhibited the highest activities of laccase and peroxidase in sugarcane bagasse with 2.6 g of YE and an increased activity of manganese peroxidase in sugarcane bagasse with 1.3 g of YE was observed. However, P. chrysosporium showed the highest activities of exoglucanase and endoglucanase in sugarcane bagasse with 1.3 g of YE. Lipid peroxidation and variations in SOD and CAT activities were observed during the production of lignocellulolytic enzymes and depending on the YE concentrations. The antioxidant defense system was induced in response to the oxidative stress caused by imbalances between the production and the detoxification of ROS.

Delignification and detoxification of peanut shell bio-waste using an extremely halophilic laccase from an Aquisalibacillus elongatus isolate

Lignocellulose bioconversion is a harsh process requiring the use of surfactants and organic solvents. Consequently, the incorporation of laccases in this bioconversion requires the bioprospecting of enzymes that can remain stable under extreme conditions. An extracellular, highly stable laccase was produced by the halophilic isolate Aquisalibacillus elongatus in submerged liquid culture fermentation. Statistical and non-statistical strategies gave the highest enzymatic activity (8.02 U mL^-1) following addition of glucose (1.7 g L^-1), copper sulfate (0.8 g L^-1), urea (15 g L^-1), and CaCl₂ (0.8 g L^-1). The enzyme, after purification using a synthetic affinity support, delignified a peanut shell substrate by 45%. A pH of 8.0 and a temperature of 35 °C were optimal for delignification of this bio-waste material. Addition of [Bmim][PF₆], 1,4-dioxane, acetone, and HBT promoted this bio-waste delignification. Bio-treatment in the presence of 50% [Bmim][PF₆] gave a maximal lignin removal of 87%. The surfactants tested had no significant effects on the delignification yield. The laccase also detoxified the toxic phenols found in peanut shell waste. The high catalytic efficiency of this enzyme against a lignocellulosic sample under extreme conditions suggests the suitability of this laccase for industrial applications.

Enhancement in multiple lignolytic enzymes production for optimized lignin degradation and selectivity in fungal pretreatment of sweet sorghum bagasse

The objective of this work was to study the increase in multiple lignolytic enzyme productions through the use of supplements in combination in pretreatment of sweet sorghum bagasse (SSB) by Coriolus versicolor such that enzymes act synergistically to maximize the lignin degradation and selectivity. Enzyme activities were enhanced by metallic salts and phenolic compound supplements in SSF. Supplement of syringic acid increased the activities of LiP, AAO and laccase; gallic acid increased MnP; CuSO₄ increased laccase and PPO to improve the lignin degradations and selectivity individually, higher than control. Combination of supplements optimized by RSM increased the production of laccase, LiP, MnP, PPO and AAO by 17.2, 45.5, 3.5, 2.4 and 3.6 folds respectively for synergistic action leading to highest lignin degradation (2.3 folds) and selectivity (7.1 folds). Enzymatic hydrolysis of pretreated SSB yielded ∼2.43 times fermentable sugar. This technique could be widely applied for pretreatment and enzyme productions.

Production of Enzymes From Agricultural Wastes and Their Potential Industrial Applications

Enzymatic hydrolysis is the significant technique for the conversion of agricultural wastes into valuable products. Agroindustrial wastes such as rice bran, wheat bran, wheat straw, sugarcane bagasse, and corncob are cheapest and plentifully available natural carbon sources for the production of industrially important enzymes. Innumerable enzymes that have numerous applications in industrial processes for food, drug, textile, and dye use have been produced from different types of microorganisms from agricultural wastes. Utilization of agricultural wastes offers great potential for reducing the production cost and increasing the use of enzymes for industrial purposes. This chapter focuses on economic production of actinobacterial enzymes from agricultural wastes to make a better alternative for utilization of biomass generated in million tons as waste annually.

Unravelling the capability of Pyrenophora phaeocomes S-1 for the production of ligno-hemicellulolytic enzyme cocktail and simultaneous bio-delignification of rice straw for enhanced enzymatic saccharification

A natural variant of Pyrenophora phaeocomes isolated from natural biodiversity was able to grow on various agricultural residues by co-producing laccase, xylanase and mannanase. Solid state fermentation of rice straw induced the highest productivities corresponding to 10,859.51±46.74, 22.01±1.00 and 10.45±0.128IUgds^-1 for laccase, xylanase and mannanase respectively after 4days. Besides producing the ligno-hemicellulolytic enzyme cocktail, 40days cultivation of P. phaeocomes S-1 on rice straw brought about the 63 and 51% degradation of lignin and hemicellulose. These components were further removed with mild alkali extraction revealing the overall losses amounting to 78 and 60% respectively for lignin, and hemicellulose. The biologically pretreated straw upon enzymatic hydrolysis revealed 50% saccharification efficiency releasing 470mgg^-1 sugars. Application of this knowledge will lead to efficient management of waste rice straw with low cost production of industrially important enzymes cocktail and its biological delignification for effective enzymatic hydrolysis to free sugars.

Biological processes for advancing lignocellulosic waste biorefinery by advocating circular economy

The actualization of a circular economy through the use of lignocellulosic wastes as renewable resources can lead to reduce the dependence from fossil-based resources and contribute to a sustainable waste management. The integrated biorefineries, exploiting the overall lignocellulosic waste components to generate fuels, chemicals and energy, are the pillar of the circular economy. The biological treatment is receiving great attention for the biorefinery development since it is considered an eco-friendly alternative to the physico-chemical strategies to increase the biobased product recovery from wastes and improve saccharification and fermentation yields. This paper reviews the last advances in the biological treatments aimed at upgrading lignocellulosic wastes, implementing the biorefinery concept and advocating circular economy.