A novel ionic liquid-tolerant Fusarium oxysporum BN secreting ionic liquid-stable cellulase: consolidated bioprocessing of pretreated lignocellulose containing residual ionic liquid

Screening of Fusarium moniliforme as Potential Fungus for Integrated Biodelignification and Consolidated Bioprocessing of Napier Grass for Bioethanol Production

A fungus capable of producing ethanol from various carbon substrates was screened for direct ethanol production from lignocellulose. Fusarium moniliforme BIOTECH 3170 produced ethanol from glucose, xylose, and cellobiose after three days with theoretical yields of 86.4%, 68.6%, and 45.4%, respectively. The coculture of glucose and xylose progressed sequentially at 79.2% of the theoretical yield, with both sugars completely consumed in five days. The solid-state consolidated bioprocessing of cellulose produced 25.2 g/L of ethanol after 20 days. After 28 days of the integrated biodelignification and consolidated bioprocessing of Napier grass at solid-state conditions, up to 10.5 g/L of ethanol was produced, corresponding to an ethanol yield of 0.032 g/g biomass. Given a sufficient carbon source, the screened fungus could produce up to 42.06 g/L ethanol. F. moniliforme BIOTECH 3170 demonstrated the characteristics of a fungus for potential ethanol production from cellulose, mixed sugars, and lignocellulosic materials.

Construction of an enzymatic shuttling compartment based on reverse micellar for bamboo biomass hydrolysis in ionic liquids

The enzymatic saccharification of regenerated lignocellulose must occur separately due to the toxicity of ionic liquids to cellulase. Therefore, it is important to develop a biocompatible IL-cellulase system which effectively achieves activation and saccharification of lignocellulose. For this purpose, a dual-phase "enzyme-shuttling compartment" was constructed in this study. Tween 80 was found to form reverse micelles in the isooctane-IL two-liquid phase, acting as a microenvironment that maintains the energetic conformation of the reactive cellulase. The activated bamboo biomass was enzymatically hydrolyzed in 20% (w/v) 1-ethyl-3-methylimidazolium dimethyl phosphate and 50 mM citrate buffer at 50 °C, achieving a high total reducing sugar yield of 71.2% and maintaining an enzymatic activity of 91.2% after 24 h. Thus, an efficient system with the simultaneous activation and saccharification of natural biomass was successfully developed in a one-pot procedure at low temperatures, ensuring large-scale biomass conversion into biofuels and biological products.

Improvement of Enzymatic Saccharification and Ethanol Production from Rice Straw Using Recycled Ionic Liquid: The Effect of Anti-Solvent Mixture

One of the major concerns for utilizing ionic liquid on an industrial scale is the cost involved in the production. Despite its proven pretreatment efficiency, expenses involved in its usage hinder its utilization. A better way to tackle this limitation could be overcome by studying the recyclability of ionic liquid. The current study has applied the Box–Behnken design (BBD) to optimize the pretreatment condition of rice straw through the usage of 1-ethyl-3-methylimidazolium acetate (EMIM-Ac) as an ionic liquid. The model predicted the operation condition with 5% solid loading at 128.4 °C for 71.83 min as an optimum pretreatment condition. Under the optimized pretreatment condition, the necessity of the best anti-solvent was evaluated among water, acetone methanol, and their combinations. The study revealed that pure methanol is the suitable choice of anti-solvent, enhancing the highest sugar yield. Recyclability of EMIM-Ac coupled with anti-solvent was conducted up to five recycles following the predicted pretreatment condition. Fermentation studies evaluated the efficacy of recycled EMIM-Ac for ethanol production with 89% more ethanol production than the untreated rice straw even after five recycles. This study demonstrates the potential of recycled ionic liquid in ethanol production, thereby reducing the production cost at the industrial level.

Bright Side of Fusarium oxysporum: Secondary Metabolites Bioactivities and Industrial Relevance in Biotechnology and Nanotechnology

Fungi have been assured to be one of the wealthiest pools of bio-metabolites with remarkable potential for discovering new drugs. The pathogenic fungi, Fusarium oxysporum affects many valuable trees and crops all over the world, producing wilt. This fungus is a source of different enzymes that have variable industrial and biotechnological applications. Additionally, it is widely employed for the synthesis of different types of metal nanoparticles with various biotechnological, pharmaceutical, industrial, and medicinal applications. Moreover, it possesses a mysterious capacity to produce a wide array of metabolites with a broad spectrum of bioactivities such as alkaloids, jasmonates, anthranilates, cyclic peptides, cyclic depsipeptides, xanthones, quinones, and terpenoids. Therefore, this review will cover the previously reported data on F. oxysporum, especially its metabolites and their bioactivities, as well as industrial relevance in biotechnology and nanotechnology in the period from 1967 to 2021. In this work, 180 metabolites have been listed and 203 references have been cited.

A Lignocellulolytic Colletotrichum sp. OH with Broad-Spectrum Tolerance to Lignocellulosic Pretreatment Compounds and Derivatives and the Efficiency to Produce Hydrogen Peroxide and 5-Hydroxymethylfurfural Tolerant Cellulases

Fungal endophytes are an emerging source of novel traits and biomolecules suitable for lignocellulosic biomass treatment. This work documents the toxicity tolerance of Colletotrichum sp. OH toward various lignocellulosic pretreatment-derived inhibitors. The effects of aldehydes (vanillin, p-hydroxybenzaldehyde, furfural, 5-hydroxymethylfurfural; HMF), acids (gallic, formic, levulinic, and p-hydroxybenzoic acid), phenolics (hydroquinone, p-coumaric acid), and two pretreatment chemicals (hydrogen peroxide and ionic liquid), on the mycelium growth, biomass accumulation, and lignocellulolytic enzyme activities, were tested. The reported Colletotrichum sp. OH was naturally tolerant to high concentrations of single inhibitors like HMF (IC50; 17.5 mM), levulinic acid (IC50; 29.7 mM), hydroquinone (IC50; 10.76 mM), and H2O2 (IC50; 50 mM). The lignocellulolytic enzymes displayed a wide range of single and mixed inhibitor tolerance profiles. The enzymes β-glucosidase and endoglucanase showed H2O2- and HMF-dependent activity enhancements. The enzyme β-glucosidase activity was 34% higher in 75 mM and retained 20% activity in 125 mM H2O2. Further, β-glucosidase activity increased to 24 and 32% in the presence of 17.76 and 8.8 mM HMF. This research suggests that the Colletotrichum sp. OH, or its enzymes, can be used to pretreat plant biomass, hydrolyze it, and remove inhibitory by-products.

Consolidated bioethanol production from olive mill waste: Wood-decay fungi from central Morocco as promising decomposition and fermentation biocatalysts

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First report on lignocellulolytic activity and diversity of fungi from central Morocco.

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Olive Mill Waste (OMW) is a suitable biomass for local biorefinery in Meknes region.

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Fusaria isolates produce high and diversified lignocellulases using Consolidated Bioprocess.

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Fusarium oxysporum (76) achieves 2.47 g.L⁻¹ bioethanol production and 0.84 g.g⁻¹ yield.

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Bioethanol is maximally produced during the oxygen-limiting phase.

Meknes region is a Moroccan olive-processing area generating high amounts of non-valorized Olive Mill Waste (OMW). Fungi are natural decomposers producing varied enzyme classes and effectively contributing to the carbon cycle. However, structural complexity of biomass and modest performances of wild fungi are major limits for local biorefineries. The objective of current research is to assess the ability of local fungi for bioethanol production from OMW using Consolidated Bioprocessing (CBP). This is done by characterizing lignocellulolytic potential of six wood-decay and compost-inhabiting ascomycetes and selecting potent fermentation biocatalysts. High and diversified activities were expressed by Fusarium solani and Fusarium oxysporum: 9.36 IU. mL⁻¹ and 2.88 IU. mL⁻¹ total cellulase activity, 0.54 IU. mL⁻¹ and 0.57 IU. mL⁻¹ laccase activity, respectively, and 8.43 IU. mL⁻¹ lignin peroxidase activity for the latter. F. oxysporum had maximum bioethanol production and yield of 2.47 g.L^-1 and 0.84 g.g⁻¹, respectively, qualifying it as an important bio-agent for single-pot local biorefinery.

Diversity of Cellulase-Producing Filamentous Fungi From Tibet and Transcriptomic Analysis of a Superior Cellulase Producer Trichoderma harzianum LZ117

Filamentous fungi are widely used for producing cellulolytic enzymes to degrade lignocellulosic biomass. Microbial resources from Tibet have received great attention due to the unique geographic and climatic conditions in the Qinghai-Tibet Plateau. However, studies on cellulase producing fungal strains originated from Tibet remain very limited, and so far no studies have been focused on regulation of cellulase production of the specific strains thereof. Here, filamentous fungal strains were isolated from soil, plant, and other environments in Tibet, and cellulase-producing strains were further investigated. A total of 88 filamentous fungal strains were identified, and screening of cellulase-producing fungi revealed that 16 strains affiliated with the genera Penicillium, Trichoderma, Aspergillus, and Talaromyces exhibited varying cellulolytic activities. Among these strains, T. harzianum isolate LZ117 is the most potent producer. Comparative transcriptome analysis using T. harzianum LZ117 and the control strain T. harzianum K223452 cultured on cellulose indicated an intensive modulation of gene transcription related to protein synthesis and quality control. Furthermore, transcription of xyr1 which encodes the global transcriptional activator for cellulase expression was significantly up-regulated. Transcription of cre1 and other predicted repressors controlling cellulase gene expression was decreased in T. harzianum LZ117, which may contribute to enhancing formation of primary cellulases. To our knowledge, this is the first report that the transcription landscape at the early enzyme production stage of T. harzianum was comprehensively described, and detailed analysis on modulation of transporters, regulatory proteins as well as protein synthesis and processing was presented. Our study contributes to increasing the catalog of publicly available transcriptome data from T. harzianum, and provides useful clues for unraveling the biotechnological potential of this species for lignocellulosic biorefinery.

An Overview on the Toxicological Properties of Ionic Liquids toward Microorganisms

Ionic liquids (ILs), a class of materials with unique physicochemical properties, have been used extensively in the fields of chemical engineering, biotechnology, material sciences, pharmaceutics, and many others. Because ILs are very polar by nature, they can migrate into the environment with the possibility of inclusion in the food chain and bioaccumulation in living organisms. However, the chemical natures of ILs are not quintessentially biocompatible. Therefore, the practical uses of ILs must be preceded by suitable toxicological assessments. Among different methods, the use of microorganisms to evaluate IL toxicity provides many advantages including short generation time, rapid growth, and environmental and industrial relevance. This article reviews the recent research progress on the toxicological properties of ILs toward microorganisms and highlights the computational prediction of various toxicity models.

Consolidated bioprocessing of surfactant-assisted ionic liquid-pretreated Parthenium hysterophorus L. biomass for bioethanol production

The current study presents the first ever report of surfactant (Tween-20) assisted ionic liquid IL, (1-ethyl-3-methylimidazolium methane sulphonate [Emim][MeSO₃]) pretreatment of Parthenium hysterophorus biomass, its saccharification by in-house developed enzyme cocktail from Aspergillus aculeatus PN14, and fermentation of sugars to bioethanol under consolidated bioprocess. Optimization of pretreatment process variables viz. biomass loading, temperature and time, resulted in enhanced sugar yield (40.1%) upon saccharification of pretreated biomass with IL-stable cellulase and xylanase enzymes from an IL-tolerant newly isolated fungus Aspergillus aculeatus PN14. Physicochemical analysis of surfactant assisted IL-pretreated biomass by SEM, FT-IR and XRD provided molecular insights into inter/intra molecular ultrastructural changes in the biomass that eased the saccharification. Thorough understanding of chemical/molecular structure of biomass may help developing customized pretreatment regimes of apt severity which might result in enhanced accessibility of enzymes to biomass, and hence more sugar content.

Ultrasound and surfactant assisted ionic liquid pretreatment of sugarcane bagasse for enhancing saccharification using enzymes from an ionic liquid tolerant Aspergillus assiutensis VS34

Ionic liquid (IL) pretreatment represents an effective strategy for effective fractionation of lignocellulosic biomass (LB) to fermentable sugars in a biorefinery. Optimization of combinatorial pretreatment of sugarcane bagasse (SCB) with IL (1-butyl-3-methylimidazolium chloride [Bmim]Cl) and surfactant (PEG-8000) resulted in enhanced sugar yield (16.5%) upon enzymatic saccharification. The saccharification enzymes (cellulase and xylanase) used in the current study were in-house produced from a novel IL-tolerant fungal strain Aspergillus assiutensis VS34, isolated from chemically polluted soil, which produced adequately IL-stable enzymes. This is the first ever report of IL-stable cellulase/xylanase enzyme from Aspergillus assiutensis. To get the mechanistic insights of combinatorial pretreatment physicochemical analysis of variously pretreated biomass was executed using SEM, FT-IR, XRD, and ¹H NMR studies. The combined action of IL, surfactant and ultrasound had very severe and distinct effects on the ultrastructure of biomass that subsequently resulted in enhanced accessibility of saccharification enzymes to biomass, and increased sugar yield.

Improvements of thermophilic enzymes: From genetic modifications to applications

Thermozymes (from thermophiles or hyperthermophiles) offer obvious advantages due to their excellent thermostability, broad pH adaptation, and hydrolysis ability, resulting in diverse industrial applications including food, paper, and textile processing, biofuel production. However, natural thermozymes with low yield and poor adaptability severely hinder their large-scale applications. Extensive studies demonstrated that using genetic modifications such as directed evolution, semi-rational design, and rational design, expression regulations and chemical modifications effectively improved enzyme's yield, thermostability and catalytic efficiency. However, mechanism-based techniques for thermozymes improvements and applications need more attention. In this review, stabilizing mechanisms of thermozymes are summarized for thermozymes improvements, and these improved thermozymes eventually have large-scale industrial applications.

Application of ionic liquid and alkali pretreatment for enhancing saccharification of sunflower stalk biomass for potential biofuel-ethanol production

Biorefining of lignocellulosic biomass to fuels/chemicals has recently gained immense research momentum. Current study reports sequential pretreatment of sunflower stalk (SFS) biomass in a combinatorial regime involving alkali (NaOH) and ionic liquid 1-butyl-3-methyl imidazolium chloride. The pretreatment enhanced the enzymatic digestibility, and resulted in increased sugar yield (163.42 mg/g biomass) as compared to standalone pretreatment using alkali (97.38 mg/g biomass) or ionic liquid (79.6 mg/g biomass). Ultrastructural and morphological analysis (FTIR and SEM) of pretreated biomass showed that the combined ionic liquid and alkali pretreatment causes more drastic alterations in the biomass ultrastructure as compared to alone ionic liquid or alkali pretreatment. Thus, combined pretreatment led to ease of enzymatic saccharification and consequent increased sugar yield, and this observation was corroborated by physicochemical analysis of the pretreated biomass. The pretreated SFS biomass was subjected to consolidated bioprocessing for its direct conversion to bioethanol in a single vessel.

Diversity of cultivable fungal endophytes in Paullinia cupana (Mart.) Ducke and bioactivity of their secondary metabolites

Paullinia cupana is associated with a diverse community of pathogenic and endophytic microorganisms. We isolated and identified endophytic fungal communities from the roots and seeds of P. cupana genotypes susceptible and tolerant to anthracnose that grow in two sites of the Brazilian Amazonia forest. We assessed the antibacterial, antitumor and genotoxic activity in vitro of compounds isolated from the strains Trichoderma asperellum (1BDA) and Diaporthe phaseolorum (8S). In concert, we identified eight fungal species not previously reported as endophytes; some fungal species capable of inhibiting pathogen growth; and the production of antibiotics and compounds with bacteriostatic activity against Pseudomonas aeruginosa in both susceptible and multiresistant host strains. The plant genotype, geographic location and specially the organ influenced the composition of P. cupana endophytic fungal community. Together, our findings identify important functional roles of endophytic species found within the microbiome of P. cupana. This hypothesis requires experimental validation to propose management of this microbiome with the objective of promoting plant growth and protection.

Efficacy of ionic liquids on the growth and simultaneous xylanase production by Sporotrichum thermophile: membrane integrity, composition and morphological investigation

Ionic liquids (ILs) are emerging as promising solvent systems for carrying out various biochemical reactions.

Enzymatic in situ saccharification of chestnut shell with high ionic liquid-tolerant cellulases from Galactomyces sp. CCZU11-1 in a biocompatible ionic liquid-cellulase media

In this study, it was the first time to report that the cellulases of Galactomyces sp. CCZU11-1 showed high activity and stability in the culture and reaction media containing IL [Mmim]DMP. Using untreated chestnut shell (CNS) as carbon source in the culture media containing IL [Mmim]DMP (5%, w/v), high activity of FPA (28.6U/mL), xylanase (186.2U/mL), and CMCase (107.3U/mL) were obtained, and 184.9mg/L of total protein was achieved. Furthermore, the changes in the structural features (crystallinity, morphology, and porosity) of the solid residue of CNS utilized with Galactomyces sp. CCZU11-1 were characterized with Fourier transform infrared spectroscopy, scanning electron microscopy, and X-ray diffraction. After was enzymatically hydrolyzed with the prepared crude enzymes in IL diluted to 20% (w/v), a high yield of reducing sugars, 62.1%, was obtained. Significantly, Galactomyces sp. CCZU11-1 showed high potential for the efficient transformation of lignocellulosic materials to glucose in a single-step process.

Advances in improving the performance of cellulase in ionic liquids for lignocellulose biorefinery

Ionic liquids (ILs) have been considered as a class of promising solvents that can dissolve lignocellulosic biomass and then provide enzymatic hydrolyzable holocellulose. However, most of available cellulases are completely or partially inactivated in the presence of even low concentrations of ILs. To more fully exploit the benefits of ILs to lignocellulose biorefinery, it is critical to improve the compatibility between cellulase and ILs. Various attempts have been made to screen natural IL-tolerant cellulases from different microhabitats. Several physical and chemical methods for stabilizing cellulases in ILs were also developed. Moreover, recent advances in protein engineering have greatly facilitated the rational engineering of cellulases by site-directed mutagenesis for the IL stability. This review is aimed to provide the first detailed overview of the current advances in improving the performance of cellulase in non-natural IL environments. New ideas from the most representative progresses and technical challenges will be summarized and discussed.