Solid state fermentation for production of microbial cellulases: Recent advances and improvement strategies

Bacterial cellulose in cosmetic innovation: A review

Bacterial cellulose (BC) emerges as a versatile biomaterial with a myriad of industrial applications, particularly within the cosmetics sector. The absence of hemicellulose, lignin, and pectin in its pure cellulose structure enables favorable interactions with both hydrophilic and hydrophobic biopolymers. This enhances compatibility with active ingredients commonly employed in cosmetics, such as antioxidants, vitamins, and botanical extracts. Recent progress in BC-based materials, which encompasses membranes, films, gels, nanocrystals, and nanofibers, highlights its significant potential in cosmetics. In this context, BC not only serves as a carrier for active ingredients but also plays a crucial role as a structural agent in formulations. The sustainability of BC production and processing is a central focus, highlighting the need for innovative approaches to strengthen scalability and cost-effectiveness. Future research endeavors, including the exploration of novel cultivation strategies and functionalization techniques, aim to maximize BC's therapeutic potential while broadening its scope in personalized skincare regimes. Therefore, this review emphasizes the crucial contribution of BC to the cosmetics sector, underlining its role in fostering innovation, sustainability, and ethical skincare practices. By integrating recent research findings and industry trends, this review proposes a fresh approach to advancing both skincare science and environmental responsibility in the cosmetics industry.

New approaches for solubilization of phosphate rocks through solid-state fermentation by optimization of oxalic acid production

This study explores the enhancement of phosphate rock (PR) solubilization through solid-state fermentation (SSF) by optimizing oxalic acid production using Aspergillus niger. Key process parameters, including the use of agro-industrial by-products (sugarcane bagasse (SCB), wheat bran (WB), soybean bran (SB)), pH levels, sucrose supplementation, and methanol addition, were systematically evaluated through sequential experimental designs. The results identified SCB and SB in a 1:1 ratio as the most effective substrate. Remarkably, the inclusion of methanol (7 %) and sucrose (0.5 %) resulted in a 3-fold increase in oxalic acid production. Under these optimized conditions, significant phosphorus solubilization of Bayóvar, Itafós, and Registro PRs was achieved, with Bayóvar rock releasing up to 12.1 g/kgds of soluble P (63.8 % efficiency). Additionally, the SSF process effectively released organic phosphorus from the agro-industrial substrates. These findings hold promise for advancing the bio-based economy and developing future industrial biofertilizers.

Biotransformation of Raw Mango Seed Waste into Bacterial Hydrolytic Enzymes Enhancement Via Solid State Fermentation Strategy

Solid waste generation is a huge contributor to environmental pollution issues, and food wastes are prominent in this category due to their large generation on a day-to-day basis. Thus, the settlement of daily food waste is one of the major constraints and needs innovative manufacturing sheme to valorize solid waste in sustainable manner. Moreover, these food wastes are rich in organic content, which has promising scope for their value-added products. In the present study, raw mango seed waste has been biotransformed to produce bacterial hydrolytic enzymes as feedstock. On investigating the impact of substrate, the highest bacterial cellulase production was recorded to be 18 IU/gds FP (filter paper) in 24 h of microbial incubation at 5 g of substrate in solid-state fermentation (SSF). Furthermore, at 40 °C and pH 6.0, 23 IU/gds FP enzyme could be produced in 24 h of SSF. Beside this, on comparing the influence of inorganic and organic nitrogen sources, urea has been found to provide better cellulase production, which yielded 28 IU/gds FP in 24 h of incubation, along with 77 IU/gds BG (β-glucosidase) and 89 IU/gds EG (endoglucanase). On the other hand, Tween-40 and Tween-80, two different surfactants, were employed at a 1.0% concentration for 24 h of incubation. It was noticed that Tween-80 showed complete enzyme activity at 24 h, which was found to be relatively superior to that of Tween-40. This study may have potential utility in enzyme production using mango seed as a food waste for various industrial applications.

Aspergillus awamori MK788209 cellulase: production, statistical optimization, pea peels saccharification and textile applications

BACKGROUND

The demand for low-cost cellulolytic enzyme synthesis is rising in the enzyme market. This work aims to produce cellulase by utilizing various agricultural wastes and investigating the use of enzyme in saccharification and textile industries.

RESULTS

Solid state fermentation (SSF) was applied to produce industrial enzymes, particularly cellulase, through utilizing Molokhia (Corchorus olitorius) stems by Aspergillus awamori MK788209 isolate. Two stages of statistical factorial designs Plackett-Burman (PB) and Central Composite Design (CCD) were applied to enhance the A. awamori MK788209 cellulase production from Molokhia stems (MS). The fold increase of enzyme production by PB followed by CCD was 2.51 and 4.86, respectively. Additionally, the A. awamori MK788209 culture filtrate was highly effective in saccharifying various agricultural wastes, particularly pea peels (PP) (yielding 98.33 mg reducing sugar/ml), due to its richness in cellulase, laccase, xylanase, pectinase, and amylase. By optimizing the three main variables; pea peel weight, culture filtrate volume added, and saccharification time by CCD, the sugar recovery from PP was enhanced, leading to a 3.44-fold increase in reducing sugar recovery (338 mg reducing sugar /ml). Furthermore, the A. awamori MK788209 culture filtrate showed high efficacy in textile applications, enhancing the roughness, weight loss, white index, and printing capability of treated cotton fabrics.

CONCLUSIONS

A. Awamori MK788209 produced cellulase which was effective in PP saccharification. The enzyme was also capable of enhancing cotton fabric properties.

Biocontrol rhizobacteria enhances growth and yield of wheat (Triticum aestivum) under field conditions against Fusarium oxysporum

The current study aimed to identify the survival of bio-control bacteria with antifungal activity against Fusarium oxysporum and assess their growth promoting activity in wheat crop field conditions. To evaluate the fungicidal activities of isolated bacteria using the dual culture method, both qualitative and quantitative bioassays were performed. Plant Growth Promoting activities such as Indole 3-Acetic Acid (IAA), phosphate solubilization, Hydrogen cyanide (HCN), and Siderophore production were assessed for three biocontrol bacterial isolates (BCB 07, BCB16, and BCB 83) out of 180 with 70% antagonistic activity against Fusarium oxysporum. Chitinase, protease, and cellulase interaction in isolates was also tested. BCB16 was selected as it had 70% antagonist activity against F. oxysporum but also had the highest PGPR (Plant Growth Promoting Rhizobacteria) traits when compared to the other two isolates. BCB16 was also tested for survival in talc powder and in wheat crop field conditions. Even after 4 months in talc powder, the survival rate remained stable. In a wheat crop field, BCB16 reduced the disease incidence of Fusarium oxysporum by 54.38%. When compared to fungus alone treatment, BCB16 increased average yield by 57% alone and 32% in challenged conditions. BCB16 was identified molecularly using the 16s rRNA gene. Bacillus amyloliquefaciens shared 97% of the deduced sequence. The sequence was submitted to genbank and assigned the accession number OM333889. Bacillus amyloliquefaciens has the potential to be used in the field as an alternative to synthetic fungicides against Fusarium oxysporum.

On-site enriched production of cellulase enzyme using rice straw waste and its hydrolytic performance evaluation through systematic dynamic modeling

The application of on-site produced cellulolytic enzymes in place of commercial enzymes towards hydrolytic preparations of reducing sugars using inexpensive lignocellulosic wastes is considered the most efficient strategy to accomplish a cost-effective biofuel production process. Along with improved production, intrinsic and systematic performance evaluation of the produced enzyme during the hydrolysis process through kinetic intervention remains a crucial requirement for achieving the improved performance of the process. With this motivation, the present study primarily deals with the nutritionally optimized production strategy of cellulases from rice straw (RS) waste using Trichoderma reesei (MTCC 164). The highest cellulase production was obtained 8.09 ± 0.32 g/l in batch mode at optimized combinations of 3.5% (w/v) RS inducer, 3.0% (w/v) lactose, and 1.5% (w/v) peptone. Production was further improved through pH-regulated (pH 5.5 to 6.5) fed-batch fermentations. The enzyme produced at pH 6 was considered for hydrolysis studies at 4 to 10% (w/w) solid loading due to reasonable exoglucanase, endoglucanase, and maximum β-glucosidase activity levels of 9.3 U/ml, 3.87 U/ml, and 2.65 U/ml respectively. Multi-reaction systematic kinetic modeling was implemented to evaluate enzyme performance during hydrolysis, and the values of inhibitory kinetic parameters (K_2r = 7.1 < K₁r = 18.5 < K₃r = 276.6) suggested that sequential conversion of cellulose to glucose by existing enzyme components was more dominant over direct conversion.

A Combined Study on Optimization, In Silico Modeling, and Genetic Modification of Large Scale Microbial Cellulase Production

Cellulase is a biocatalyst that hydrolyzes cellulosic biomass and is considered a major group of industrial enzymes for its applications. Extensive work has been done on microbial cellulase but fungi are considered a novel strain for their maximum cellulase production. Production cost and novel microbial strains are major challenges for its improvement where cheap agro wastes can be essential sources of cellulose as substrates. The researcher searches for more cellulolytic microbes from natural sources but the production level of isolated strains is comparatively low. So genetic modification or mutation can be employed for large-scale cellulase production before optimization. After genetic modification than in silico molecular modeling can be evaluated for substrate molecule's binding affinity. In this review, we focus not only on the conventional methods of cellulase production but also on modern biotechnological approaches applied to cellulase production by a sequential study on common cellulase-producing microbes, modified microbes, culture media, carbon sources, substrate pretreatment process, and the importance of optimum pH and temperature on fermentation. In this review, we also compare different cellulase activity determination methods. As a result, this review provides insights into the interrelationship between the characteristics of optimizing different culture conditions, genetic modification, and in silico enzyme modeling for the production of cellulase enzymes, which may aid in the advancement of large-scale integrated enzyme manufacturing of substrate-specific enzymes.

Cellulase Immobilization on Nanostructured Supports for Biomass Waste Processing

Nanobiocatalysts, i.e., enzymes immobilized on nanostructured supports, received considerable attention because they are potential remedies to overcome shortcomings of traditional biocatalysts, such as low efficiency of mass transfer, instability during catalytic reactions, and possible deactivation. In this short review, we will analyze major aspects of immobilization of cellulase-an enzyme for cellulosic biomass waste processing-on nanostructured supports. Such supports provide high surface areas, increased enzyme loading, and a beneficial environment to enhance cellulase performance and its stability, leading to nanobiocatalysts for obtaining biofuels and value-added chemicals. Here, we will discuss such nanostructured supports as carbon nanotubes, polymer nanoparticles (NPs), nanohydrogels, nanofibers, silica NPs, hierarchical porous materials, magnetic NPs and their nanohybrids, based on publications of the last five years. The use of magnetic NPs is especially favorable due to easy separation and the nanobiocatalyst recovery for a repeated use. This review will discuss methods for cellulase immobilization, morphology of nanostructured supports, multienzyme systems as well as factors influencing the enzyme activity to achieve the highest conversion of cellulosic biowaste into fermentable sugars. We believe this review will allow for an enhanced understanding of such nanobiocatalysts and processes, allowing for the best solutions to major problems of sustainable biorefinery.

Kinetic model supported improved and optimized submerged production strategy of cellulase enzyme from newspaper waste biomass

A systematic evaluation of microorganism's potential towards biosynthesis of cellulases from inexpensive lignocellulosic feedstock through appropriate kinetic modelling facilitates understanding, optimization and designing of an effective industrial cellulase enzyme production process. The present study aims to optimize a submerged fungal cultivation strategy for cellulase production from abundantly available newspaper wastes (NPW). A combined pretreatment strategy consisting diluted, 1% (v v^-1) H₂SO₄ followed by 2% (w v^-1) NaOH treatment was highly effective to convert newspaper waste to an effective cellulose-enriched inducer for the production of cellulase. In addition, the composition of the most influential nutrient components like peptone and lactose was optimized with the help of response surface methodology for enhanced cellulase production with maximum activity levels. Maximum cellulase production of 8.64 g L^-1 with 7.82 FPU mL^-1 total activity levels was achieved from optimized composition of pretreated NPW 3.29% (w v^-1), lactose 2.94% (w v^-1) and peptone 1.53% (w v^-1). To analyse intrinsic inhibition effect of the substrate concentration on cellulase production, modified Luedeking-Piret model simulated experiments were further conducted with 1.5% (w/v), 3.29% (w/v) and 4% (w/v) NPW concentrations. The developed kinetic model perfectly captured the trends of biomass production, substrate consumption and adsorption characteristic of cellulase enzyme on its activity during production. The rate constant for cellulase synthesis was evaluated to be increased to 0.040 IU g^-1 h ^-1 at 3.29% (w v^-1) of NPW concentration; however, it was further reduced to 0.024 IU g^-1 h ^-1 at higher NPW concentration of 4% (w v^-1).

A critical review on exploitation of agro-industrial biomass as substrates for the therapeutic microbial enzymes production and implemented protein purification techniques

Annually, a huge amount of waste is generated by the industries that use agricultural biomass. Researchers have looked into employing this cheap and renewable agro-biomass as a substrate for enzyme production via fermentation processes to meet the ever-increasing worldwide need. Although there are a number of sources for enzyme extraction, microbial sources have dominated industrial sectors due to their easy availability and rapid growth. Microbial enzymes are currently used in a variety of industries, including pharmaceuticals, food, biofuels, textiles, paper, detergents, and so on, and using these nutritious feedstocks not only reduces production costs but also helps to reduce environmental concerns. The present review focuses on the therapeutic microbial enzymes produced using different agro-industrial biomass as raw materials, with down-streaming techniques for obtaining a final pure product. Additionally, the article also discussed biomass pretreatment processes, including physical, chemical and biological. The type of pretreatment method to be used is mostly governed by the intended use of the major molecular components of biomass (cellulose, hemicelluloses and lignin). Finally, purification challenges are included. All of this information will be useful in the industrial synthesis of high-purity targeted enzymes if the crucial aspects that have been discussed are taken into account.

Application of solid-state fermentation by microbial biotechnology for bioprocessing of agro-industrial wastes from 1970 to 2020: A review and bibliometric analysis

This paper reviews the pertinent literature from 1970 to 2020 and presents a bibliometric analysis of research trends in the application of solid-state fermentation in the bioprocessing of agro-industrial wastes. A total 5630 publications of studies on solid-state fermentation that comprised of 5208 articles (92.50%), 340 book chapters (6.04%), 39 preprints (0.69%), 32 proceedings (0.56%), 8 edited books (0.14%) and 3 monographs (0.05%) were retrieved from Dimensions database. A review of the literature indicated that (i) fermentation of solid substrates is variously defined in the literature over the past 50 years, where "solid-state fermentation" is the most dominant research term used, and (ii) key products derived from the valorization of agro-industrial wastes through solid-state fermentation include, among others, enzymes, antioxidants, animal feed, biofuel, organic acids, biosurfactants, etc. Bibliometric analyses with VOSviewer revealed an astronomic increase in publications between 2000 and 2020, and further elucidated the most frequently explored core research topics, the most highly cited publications and authors, and countries/regions with the highest number of citations. The most cited publication between 2010 and 2020 had 382 citations compared to 725 citations for the most cited publication from 1970 to 2020. Ashok Pandey from India was the most published and cited author with 123 publications and 8,613 citations respectively; whereas Bioresource Technology was the most published and cited journal with 233 publications and 12,394 citations. Countries with the most publications and citations are Brazil, France, India, and Mexico. These findings suggest that research in the application of solid-state fermentation for bioprocessing of agro-industrial wastes has gained prominence over the past 50 years. Future perspectives and implications are discussed.

Evaluation of Blend Production of Cellulases and Xylanases Using Pretreated and Recycled Carnauba Straw

Carnauba (Copernicia prunifera) is a Brazilian palm tree used for wax production, which usually generates a large amount of waste. This work evaluated the carnauba waste for cellulase and xylanase production using Trichoderma reesei CCT2768 through a solid-state fermentation (SSF). Carnauba waste was used in its crude form (C-IN), pretreated (C-P) with alkaline hydrogen peroxide (AHP), and also recycled after the SSF process (C-PR). C-IN, C-P, and C-PR were characterized by XRD, FTIR, and SEM. Cellulase and xylanase production was performed by SSF for 72 h, and the enzymatic extracts obtained were mixed each other in different concentrations. FPase, CMCase, and xylanase activities were determined. Trichoderma reesei CCT-2768 has shown high performance to produce cellulases and xylanases. Total cellulase, CMCase, and β-glycosidase presented a highest activity when C-PPR1 (25% of C-PR and 75% of C-P) was used as a carbon source, with yield of 2.85 U/g, 41.21 U/g, and 2.80 U/g, respectively. The highest xylanase production was achieved when only the pretreated carnauba waste (C-P) was used, with an enzyme activity of 224.93 U/g. Carnauba has shown a promising carbon source capacity to induce the production of cellulolytic and xylanolytic enzymes by using T. reesei CCT2768, promoting the circular and ecofriendly economy, as well as a cost reduction, of the production process of these enzymes.

An overview of walnuts application as a plant-based

The plant-based refers to plant-based raw materials or products that are available as the source of protein and fat. Utilization and development of walnuts as a plant-based, resulting in a high-quality protein-rich walnut plant-based product: walnut protein powder and walnut peptides. Progress in research on the application of walnuts as a plant-based has been advanced, solving the problem of wasted resources and environmental pollution caused by the fact that walnut residue, a product of walnuts after oil extraction, is often thrown away as waste, or becomes animal feed or compost. This paper reviews and summarizes the research and reports on walnut plant-based at home and abroad, focusing on the application of walnut plant-based in the preparation process (enzymatic and fermentation methods) and the biological activity of the walnut protein and walnut peptide, to provide a theoretical basis for the further processing of walnuts as a walnut plant-based. It can make full use of walnut resources and play its nutritional and health care value, develop and build a series of walnut plant-based products, improve the competitiveness of walnut peptide products, turn them into treasure, and provide more powerful guidance for the development of food and medicine health industry in Yunnan.

Impact of solid-state fermentation on factors and mechanisms influencing the bioactive compounds of grains and processing by-products

Cereal and legume grains and their processing by-products are rich sources of bioactives such as phenolics with considerable health potential, but these bioactives suffer from low bioaccessibility and bioavailability, resulting in limited use. Several studies have demonstrated that solid-state fermentation (SSF) with food-grade microorganisms is effective in releasing bound phenolic compounds in cereal and legume products. In this review, we discuss the effect of SSF on cereal and legume grains and their by-products by examining the role of specific microorganisms, their hydrolytic enzymes, fermentability of agri-food substrates, and the potential health benefits of SSF-enhanced bioactive compounds. SSF with fungi (Aspergillus spp. and Rhizopus spp.), bacteria (Bacillus subtilis and lactic acid bacteria (LAB) spp.) and yeast (Saccharomyces cerevisiae) significantly increased the bioactive phenolics and antioxidant capacities in cereal and legume grains and by-products, mainly through carbohydrate-cleaving enzymes. Increased bioactive phenolic and peptide contents of SSF-bioprocessed cereal and legume grains have been implicated for improved antioxidant, anti-inflammatory, anti-carcinogenic, anti-diabetic, and angiotensin-converting-enzyme (ACE) inhibitory effects in fermented agri-food products, but these remain as preliminary results. Future research should focus on the microbial mechanisms, suitability of substrates, and the physiological health benefits of SSF-treated grains and by-products.

Thermostable Cellulases / Xylanases From Thermophilic and Hyperthermophilic Microorganisms: Current Perspective

The bioconversion of lignocellulose into monosaccharides is critical for ensuring the continual manufacturing of biofuels and value-added bioproducts. Enzymatic degradation, which has a high yield, low energy consumption, and enhanced selectivity, could be the most efficient and environmentally friendly technique for converting complex lignocellulose polymers to fermentable monosaccharides, and it is expected to make cellulases and xylanases the most demanded industrial enzymes. The widespread nature of thermophilic microorganisms allows them to proliferate on a variety of substrates and release substantial quantities of cellulases and xylanases, which makes them a great source of thermostable enzymes. The most significant breakthrough of lignocellulolytic enzymes lies in lignocellulose-deconstruction by enzymatic depolymerization of holocellulose into simple monosaccharides. However, commercially valuable thermostable cellulases and xylanases are challenging to produce in high enough quantities. Thus, the present review aims at giving an overview of the most recent thermostable cellulases and xylanases isolated from thermophilic and hyperthermophilic microbes. The emphasis is on recent advancements in manufacturing these enzymes in other mesophilic host and enhancement of catalytic activity as well as thermostability of thermophilic cellulases and xylanases, using genetic engineering as a promising and efficient technology for its economic production. Additionally, the biotechnological applications of thermostable cellulases and xylanases of thermophiles were also discussed.

Bioprospecting of cowdung microflora for sustainable agricultural, biotechnological and environmental applications

The review aims at highlighting the manifold applications of cow dung (CD) and CD microflora covering agricultural, biotechnological and environmental applications. The update research on CD microflora and CD in agricultural domain such as biocontrol, growth promotion, organic fertilizer, sulfur oxidation, phosphorus solubilization, zinc mobilization and underlying mechanisms involved in these processes are discussed. The significance of CD applications in tropical agriculture in context to climate change is briefly emphasized. The advances on genomics and proteomics of CD microflora for enhanced yield of enzymes, organic acids, alternative fuels (biomethane and biohydrogen) and other biocommodities, and environmental applications in context to biosorption of heavy metals, biodegradation of xenobiotics, etc. have been given critical attention.

Solid-state fermented brewer's spent grain enzymatic extract increases in vitro and in vivo feed digestibility in European seabass

Brewer's spent grain (BSG) is the largest by-product originated from the brewery industry with a high potential for producing carbohydrases by solid-state fermentation. This work aimed to test the efficacy of a carbohydrases-rich extract produced from solid-state fermentation of BSG, to enhance the digestibility of a plant-based diet for European seabass (Dicentrarchus labrax). First, BSG was fermented with A. ibericus to obtain an aqueous lyophilized extract (SSF-BSG extract) and incorporated in a plant-based diet at increasing levels (0-control; 0.1%, 0.2%, and 0.4%). Another diet incorporating a commercial carbohydrases-complex (0.04%; Natugrain; BASF) was formulated. Then, all diets were tested in in vitro and in vivo digestibility assays. In vitro assays, simulating stomach and intestine digestion in European seabass, assessed dietary phosphorus, phytate phosphorus, carbohydrates, and protein hydrolysis, as well as interactive effects between fish enzymes and dietary SSF-BSG extract. After, an in vivo assay was carried out with European seabass juveniles fed selected diets (0-control; 0.1%, and 0.4%). In vitro digestibility assays showed that pentoses release increased 45% with 0.4% SSF-BSG extract and 25% with Natugrain supplemented diets, while amino acids release was not affected. A negative interaction between endogenous fish enzymes and SSF-BSG extract was observed in both diets. The in vivo digestibility assay corroborated in vitro data. Accordingly, the dietary supplementation with 0.4% SSF-BSG increased the digestibility of dry matter, starch, cellulose, glucans, and energy and did not affect protein digestibility. The present work showed the high potential of BSG to produce an added-value functional supplement with high carbohydrases activity and its potential contribution to the circular economy by improving the nutritional value of low-cost and sustainable ingredients that can be included in aquafeeds.

Technological advances for improving fungal cellulase production from fruit wastes for bioenergy application: A review

Fruit wastes can be imperative to elevate economical biomass to biofuels production process at pilot scale. Because of the renewable features, huge availability, having low lignin content organic nature and low cost; these wastes can be of much interest for cellulase enzyme production. This review provides recent advances on the fungal cellulase production using fruit wastes as a potential substrate. Also, the availability of fruit wastes, generation and processing data and their potential applications for cellulase enzyme production have been discussed. Several aspects, including cellulase and its function, solid-state fermentation, process parameters, microbial source, and the application of enzyme in biofuels industries have also been discussed. Further, emphasis has been made on various bottlenecks and feasible approaches such as use of nanomaterials, co-culture, molecular techniques, genetic engineering, and cost economy analysis to develop a low-cost based comprehensive technology for viable production of cellulase and its application in biofuels production technology.

Improvement of cellulase and xylanase production in Penicillium oxalicum under solid-state fermentation by flippase recombination enzyme/ recognition target-mediated genetic engineering of transcription repressors

Penicillium oxalicum has received increasing attention as a potential cellulase-producer. In this study, a copper-controlled flippase recombination enzyme/recognition target (FLP/FRT)-mediated recombination system was constructed in P. oxalicum, to overcome limited availability of antibiotic resistance markers. Using this system, two crucial transcription repressor genes atf1 and cxrC for the production of cellulase and xylanase under solid-state fermentation (SSF) were simultaneously deleted, thereby leading to 2.4- to 29.1-fold higher cellulase and 78.9% to 130.8% higher xylanase production than the parental strain under SSF, respectively. Glucose and xylose released from hydrolysis of pretreated sugarcane bagasse achieved 10.6%-13.5% improvement by using the crude enzymes from the engineered strain Δatf1ΔcxrC::flp under SSF in comparison with that of the parental strain. Consequently, these results provide a feasible strategy for improved cellulase and xylanase production by filamentous fungi.

Integration of Solid State and Submerged Fermentations for the Valorization of Organic Municipal Solid Waste

Solid state fermentation (SsF) is recognized as a suitable process for the production of enzymes using organic residues as substrates. However, only a few studies have integrated an evaluation of the feasibility of applying enzymes produced by SsF into subsequent hydrolyses followed by the production of target compounds, e.g., lactic acid (LA), through submerged-liquid fermentations (SmF). In this study, wheat bran (WB) was used as the substrate for the production of enzymes via SsF by Aspergillus awamori DSM No. 63272. Following optimization, cellulase and glucoamylase activities were 73.63 ± 5.47 FPU/g_ds and 107.10 ± 2.63 U/g_db after 7 days and 5 days of fermentation, respectively. Enzymes were then used for the hydrolysis of the organic fraction of municipal solid waste (OFMSW). During hydrolysis, glucose increased considerably with a final value of 19.77 ± 1.56 g/L. Subsequently, hydrolysates were fermented in SmF by Bacillus coagulans A166 increasing the LA concentration by 15.59 g/L. The data reported in this study provides an example of how SsF and SmF technologies can be combined for the valorization of WB and OFMSW.

Analysis of Engineered Tobacco Mosaic Virus and Potato Virus X Nanoparticles as Carriers for Biocatalysts

Plant virus nanoparticles are promising candidates for the development of novel materials, including nanocomposites and scaffolds/carriers for functional molecules such as enzymes. Their advantages for enzyme immobilization include a modular organization, a robust and programmable structure, and a simple, cost-effective production. However, the activity of many enzymes relies on posttranslational modification and most plant viruses replicate in the cytoplasm, so functional enzymes cannot be displayed on the virus surface by direct coat protein fusions. An alternative display system to present the Trichoderma reesei endoglucanase Cel12A on potato virus X (PVX) using SpyTag/SpyCatcher (ST/SC) technology was recently developed by the authors, which allows the carrier and enzyme to be produced separately before isopeptide conjugation. Although kinetic analysis clearly indicated efficient biocatalyst activity, the PVX carrier interfered with substrate binding. To overcome this, the suitability of tobacco mosaic virus (TMV) was tested, which can also accommodate a larger number of ST peptides. We produced TMV particles displaying ST as a new platform for the immobilization of enzymes such as Cel12A, and compared its performance to the established PVX-ST platform in terms of catalytic efficiency. Although more enzyme molecules were immobilized on the TMV-ST particles, we found that the rigid scaffold and helical spacing significantly affected enzyme activity.

Obtaining Antioxidants and Natural Preservatives from Food By-Products through Fermentation: A Review

Industrial food waste has potential for generating income from high-added-value compounds through fermentation. Solid-state fermentation is promising to obtain a high yield of bioactive compounds while requiring less water for the microorganism’s growth. A number of scientific studies evinced an increase in flavonoids or phenolics from fruit or vegetable waste and bioactive peptides from cereal processing residues and whey, a major waste of the dairy industry. Livestock, fish, or shellfish processing by-products (skin, viscera, fish scales, seabass colon, shrimp waste) also has the possibility of generating antioxidant peptides, hydrolysates, or compounds through fermentation. These bioactive compounds (phenolics, flavonoids, or antioxidant peptides) resulting from bacterial or fungal fermentation are also capable of inhibiting the growth of commonly occurring food spoilage fungi and can be used as natural preservatives. Despite the significant release or enhancement of antioxidant compounds through by-products fermentation, the surface areas of large-scale bioreactors and flow patterns act as constraints in designing a scale-up process for improved efficiency. An in-process purification method can also be the most significant contributing factor for raising the overall cost. Therefore, future research in modelling scale-up design can contribute towards mitigating the discard of high-added-value generating residues. Therefore, in this review, the current knowledge on the use of fermentation to obtain bioactive compounds from food by-products, emphasizing their use as natural preservatives, was evaluated.

Cellulases: From Bioactivity to a Variety of Industrial Applications

Utilization of microbial enzymes has been widely reported for centuries, but the commercial use of enzymes has been recently adopted. Particularly, cellulases have been utilized in various commercial sectors including agriculture, brewing, laundry, pulp and paper and textile industry. Cellulases of microbial origin have shown their potential application in various commercial sectors including textile, pulp and paper, laundry, brewing, agriculture and biofuel. Cellulases have diversified applications in the food industry, food service, food supply and its preservation. Indeed, cellulases can tenderize fruits, clarify the fruit juices, reduce roughage in dough, hydrolyze the roasted coffee, extract tea polyphenols and essential oils from olives and can increase aroma and taste in food items. However, their role in food industries has by and large remained neglected. The use of immobilized cellulases has further expanded their application in fruit and vegetable processing as it potentiates the catalytic power and reduces the cost of process. Technological and scientific developments will further expand their potential usage in the food industry.

Bioreactor and Bioprocess Design Issues in Enzymatic Hydrolysis of Lignocellulosic Biomass

Saccharification of lignocellulosic biomass is a fundamental step in the biorefinery of second generation feedstock. The physicochemical and enzymatic processes for the depolymerization of biomass into simple sugars has been achieved through numerous studies in several disciplines. The present review discusses the development of technologies for enzymatic saccharification in industrial processes. The kinetics of cellulolytic enzymes involved in polysaccharide hydrolysis has been discussed as the starting point for the design of the most promising bioreactor configurations. The main process configurations—proposed so far—for biomass saccharification have been analyzed. Attention was paid to bioreactor configurations, operating modes and possible integrations of this operation within the biorefinery. The focus is on minimizing the effects of product inhibition on enzymes, maximizing yields and concentration of sugars in the hydrolysate, and reducing the impact of enzyme cost on the whole process. The last part of the review is focused on an emerging process based on the catalytic action of laccase applied to lignin depolymerization as an alternative to the consolidated physicochemical pretreatments. The laccases-based oxidative process has been discussed in terms of characteristics that can affect the development of a bioreactor unit where laccases or a laccase-mediator system can be used for biomass delignification.

Production of Lignocellulolytic Enzymes and Biomass of Trametes versicolor from Agro-Industrial Residues in a Novel Fixed-Bed Bioreactor with Natural Convection and Forced Aeration at Pilot Scale

Solid-state fermentation requires the development of more efficient cultivation systems for its industrial application. The objective of this work was to evaluate the effect of aeration regime on the production of biomass and several lignocellulolytic enzymes (laccase, manganese peroxidase, endoxylanase, β-glucosidase, and total cellulases) by Trametes versicolor in a novel fixed-bed solid-state pilot-scale bioreactor. Three regimes were assessed: natural convection, low aeration level (10 min every 6 h at 10 L/h air flowrate), and high aeration level (1 h every 6 h at 10 L/h air flowrate). The mushroom was grown on a medium based on lignocellulosic residues. The design of the bioreactor, as well as the control of aeration, humidity, and temperature of the beds, allowed T. versicolor to grow properly on the medium, reaching a maximum biomass production of 204.7 mg/g dry solid (ds). The influence that aeration regime had on the production of lignocellulolytic enzymes was determined. Low level of forced aeration favored obtaining the highest titers of laccase (6.37 U/g ds) compared to natural convection and high aeration level. The greatest lignin degradation was also verified for low aeration regime. For the first time, pilot scale cultivation of T. versicolor was reported in a fixed-bed bioreactor.

Bioprospecting of microbial strains for biofuel production: metabolic engineering, applications, and challenges

The issues of global warming, coupled with fossil fuel depletion, have undoubtedly led to renewed interest in other sources of commercial fuels. The search for renewable fuels has motivated research into the biological degradation of lignocellulosic biomass feedstock to produce biofuels such as bioethanol, biodiesel, and biohydrogen. The model strain for biofuel production needs the capability to utilize a high amount of substrate, transportation of sugar through fast and deregulated pathways, ability to tolerate inhibitory compounds and end products, and increased metabolic fluxes to produce an improved fermentation product. Engineering microbes might be a great approach to produce biofuel from lignocellulosic biomass by exploiting metabolic pathways economically. Metabolic engineering is an advanced technology for the construction of highly effective microbial cell factories and a key component for the next-generation bioeconomy. It has been extensively used to redirect the biosynthetic pathway to produce desired products in several native or engineered hosts. A wide range of novel compounds has been manufactured through engineering metabolic pathways or endogenous metabolism optimizations by metabolic engineers. This review is focused on the potential utilization of engineered strains to produce biofuel and gives prospects for improvement in metabolic engineering for new strain development using advanced technologies.

Production of Gloeophyllum trabeum Endoglucanase Cel12A in Nicotiana benthamiana for Cellulose Degradation

Lignocellulosic biomass from plants has been used as a biofuel source and the potent acidic endoglucanase GtCel12A has been isolated from Gloeophyllum trabeum, a filamentous fungus. In this study, we established a plant-based platform for the production of active GtCel12A fused to family 3 cellulose-binding module (CBM3). We used the signal sequence of binding immunoglobulin protein (BiP) and the endoplasmic reticulum (ER) retention signal for the accumulation of the produced GtCel12A in the ER. To achieve enhanced enzyme expression, we incorporated the M-domain of the human receptor-type tyrosine-protein phosphatase C into the construct. In addition, to enable the removal of N-terminal domains that are not necessary after protein expression, we further incorporated the cleavage site of Brachypodium distachyon small ubiquitin-like modifier. The GtCel12A-CBM3 fusion protein produced in the leaves of Nicotiana benthamiana exhibited not only high solubility but also efficient endoglucanase activity on the carboxymethyl cellulose substrate as determined by 3,5-dinitrosalicylic acid assay. The endoglucanase activity of GtCel12A-CBM3 was maintained even when immobilized on microcrystalline cellulose beads. Taken together, these results indicate that GtCel12A endoglucanase produced in plants might be used to provide monomeric sugars from lignocellulosic biomass for bioethanol production.

Optimization of cellulase production by Bacillus subtilis subsp. subtilis JJBS300 and biocatalytic potential in saccharification of alkaline-pretreated rice straw

Optimization of cellulase production by Bacillus subtilis subsp. subtilis JJBS300 resulted in maximum cellulase (CMCase 9.7 U/g substrate) using wheat bran and rice straw in 1:1 ratio at substrate to moisture ratio of 1:3 at 35 °C and pH 4.0 after 48 h. Partially purified cellulase of B. subtilis subsp. subtilis showed optimal activity at 50 °C and pH 5.0. Among the metal ions, Na⁺, Ca²⁺ and Fe²⁺ stimulated the cellulase activity. Glutaraldehyde and 1-butanol also enhanced the cellulase activity as compared to other solvents. Bacterial cellulase hydrolyzed ammonia-pretreated rice straw more efficiently as compared to sodium-carbonate pretreated and untreated biomass. Optimization of saccharification of untreated and pretreated (sodium carbonate and ammonia) rice straw by bacterial cellulase resulted in high liberation of reducing sugars with enzyme dose of 100 U/g substrate (221 mg/g substrate) at pH 5.0 (103 mg/g substrate) and 50 °C (142 mg/g substrate) after 6 h in ammonia-pretreated rice straw. Furthermore, liberation of reducing sugars increased with incubation time showing maximum reducing sugars (171 mg/g substrate) after 24 h in ammonia-pretreated rice straw. HPLC analysis of enzymatic hydrolysate of ammonia-pretreated rice straw verified the ability of bacterial cellulase in liberation of various monomeric and oligomeric sugars.

Solid state fermentation of Moringa oleifera leaf meal by mixed strains for the protein enrichment and the improvement of nutritional value

Moringa oleifera Lam. (MO) is a fast-growing multi-purpose deciduous tree with high biomass and nutritional value. However, the presence of antinutritional factors, poor palatability, and indigestibility of Moringa oleifera leaf meal (MOLM) restrict its application to animal feed. This study aimed to obtain high-quality protein feeds via solid-state fermentation (SSF) of MOLM. The process conditions for increasing the true protein (TP) content using Aspergillus niger, Candida utilis and Bacillus subtilis co-cultures were optimized, and the chemical composition of MOLM was compared before and after fermentation. The results of this study showed that the highest TP content could be obtained through mixed-strain culture of A. niger, C. utilis and B. subtilis at a ratio of 1:1:2. The MOLM was inoculated with A. niger, followed by C. utilis and B. subtilis 24 h later. The optimized co-culture parameters were as follows: total inoculation size, 24%; temperature, 32 °C; fermentation time, 6.5 days; and initial water content, 60%. The maximum TP yield was 28.37%. Notably, in the fermented MOLM (FMOLM), the content of nutrients such as crude protein (CP), small peptides, and total amino acids (AAs) were significantly increased relative to unfermented MOLM, whereas the contents of crude fiber (CF), tannin, and phytic acid were significantly decreased. MOLM analysis using scanning electron microscopy (SEM) revealed that SSF disrupted the surface structure of MOLM, and sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE) indicated that macromolecular proteins were degraded. The in vitro protein digestibility (IVPD) of FMOLM was also improved significantly. Our findings suggest that multi-strain fermentation with A. niger, C. utilis and B. subtilis improves the nutritional quality of MOLM, rendering it a viable functional feedstuff for use in livestock industries in the future.

Isolation and Selection of Streptomyces Species from Semi-arid Agricultural Soils and Their Potential as Producers of Xylanases and Cellulases

The Mezquital Valley (MV), Mexico, is a semi-arid region whose main economic activity is agriculture, this zone is characterized by the use of wastewater for crop irrigation. This condition has increased the amount nutrients in soils, organic carbon content and native microorganisms. The Streptomyces species are a group of saprophytic bacteria that represent between 20 and 60% of the total microbial population in soils, capable of producing metabolites of commercial importance. In this work, Streptomyces species were isolated from agricultural soils of the MV and was evaluated the production of endoglucanases (CMCase) and xylanases (Xyl) in Solid-State Cultivation (SSC). From soil samples, 73 possible strains of Streptomyces species were isolated for their ability to produce CMCase and Xyl in SSC. The study also included its characterization by morphological characteristics. Of the isolated microorganisms, 38 strains were selected as strong enzyme producers according to the measurement of the halo generated in plate and by growth on barley straw as only carbon source. Two different sizes of barley straw particle were tested, finding that the greatest enzymatic activity was observed in particle size 12. Three strains of Streptomyces species were chosen which presented the best catalytic capacities, a maximum of 100.69 AU Xyl/gram dry matter (gdm), 82 AU Xyl/gdm and 26.02 AU CMCase/gdm for strains 30, 28 and 12, respectively. The strains were identified by ribosomal gen16s sequence and identified as S. flavogriseus, S. virginiae and S. griseoaurantiacus. It is the first report of endogluconase and xylanolytic activity by S. virginiae isolated from a semi-arid soil.

Production and characterization of an enzyme extract with cellulase activity produced by an indigenous strain of Fusarium verticillioides ITV03 using sweet sorghum bagasse

OBJECTIVES

To evaluate a strain of Fusarium verticillioides ITV03 isolated from wood residues in the Veracruz region of Mexico. Endoglucanase and β-glucosidase production by submerged fermentation was optimized using a Box-Behnken design, where the independent variables were urea, ammonium sulfate and yeast extract.

RESULTS

After optimization, an endoglucanase activity of 0.27 U/mL was achieved; subsequently, three carbon sources were evaluated (carboxymethyl cellulose, sweet sorghum bagasse cellulose and delignified sweet sorghum bagasse (DSSB). The results showed that DSSB yielded the greatest endoglucanase (0.28 U/mL) and β-glucosidase (0.12 U/mL) activities. Both enzymatic activities were characterized for the effect of pH, temperature and thermostability. The optimal parameters of β-glucosidase and endoglucanase activity were pH 5 and 4 respectively, the optimum temperature 60 °C. These enzymes were stable at 50 °C for 150.68 h and 8.54 h, with an activation energy (E_a(day)) of 265.55 kJ/mol and 44.40 kJ/mol respectively, for β-glucosidase and endoglucanase.

CONCLUSION

The present work shows that a native strain like F. verticillioides ITV03 using DSSB supplemented with nitrogen has a great potential as a producer of cellulase for lignocellulosic residue hydrolysis.

Bioethanol Production from Food Waste Applying the Multienzyme System Produced On-Site by Fusarium oxysporum F3 and Mixed Microbial Cultures

Waste management and production of clean and affordable energy are two main challenges that our societies face. Food waste (FW), in particular, can be used as a feedstock for the production of ethanol because of its composition which is rich in cellulose, hemicellulose and starch. However, the cost of the necessary enzymes used to convert FW to ethanol remains an obstacle. The on-site production of the necessary enzymes could be a possible solution. In the present study, the multienzyme production by the fungus Fusarium oxysporum F3 under solid state cultivation using different agroindustrial residues was explored. Maximum amylase, glucoamylase, endoglucanase, b-glucosidase, cellobiohydrolase, xylanase, b-xylosidase and total cellulase titers on wheat bran (WB) were 17.8, 0.1, 65.2, 27.4, 3.5, 221.5, 0.7, 0.052 and 1.5 U/g WB respectively. F. oxysporum was used for the hydrolysis of FW and the subsequent ethanol production. To boost ethanol production, mixed F. oxysporum and S. cerevisiae cultures were also used. Bioethanol production by F. oxysporum monoculture reached 16.3 g/L (productivity 0.17 g/L/h), while that of the mixed culture was 20.6 g/L (productivity 1.0 g/L/h). Supplementation of the mixed culture with glucoamylase resulted in 30.3 g/L ethanol with a volumetric productivity of 1.4 g/L/h.

Two Phase Anaerobic Digestion System of Municipal Solid Waste by Utilizing Microaeration and Granular Activated Carbon

In an anaerobic digestion (AD) process, the hydrolysis phase is often limited when substrates with high concentrations of solids are used. We hypothesized that applying micro-aeration in the hydrolysis phase and the application of granular activated carbon (GAC) in the methanogenesis phase could make the AD process more efficient. A packed bed reactor (PBR) coupled with an up-flow anaerobic sludge blanket (UASB) was conducted, and its effects on methane generation were evaluated. The micro-aeration rate applied in PBR was 254 L-air/kg-Total solids (TS)-d was compared with a control reactor. Micro-aeration showed that it reduced the hydrolysis time and increased the organic matter solubilization as chemical oxygen demand (COD) increasing 200%, with a volatile fatty acids (VFAs) increment higher than 300%, compared to the control reactor (without aeration). Our findings revealed that the implementations of microaeration and GAC in the two-phase AD system could enhance methane production by reducing hydrolysis time, increasing solid waste solubilization.