Morphological variation and expressed sequence tags-simple sequence repeats-based genetic diversity of Aspergillus cristatus in Chinese dark tea

Introduction

Aspergillus cristatus is a homothallic fungus that is used in the natural fermentation process of Chinese Fuzhuan tea and has been linked to the production of bioactive components. However, not much is known about the variations present in the fungus. To understand the variation of the dominant microorganism, A. cristatus, within dark tea, the present study investigated the genetic and morphological diversity of 70 A. cristatus collected across six provinces of China.

Methods

Expressed sequence tags-simple sequence repeats (EST-SSR) loci for A. cristatus were identified and corresponding primers were developed. Subsequently, 15 specimens were selected for PCR amplification.

Results

The phylogenetic tree obtained revealed four distinct clusters with a genetic similarity coefficient of 0.983, corresponding to previously identified morphological groups. Five strains (A1, A11, B1, D1, and JH1805) with considerable differences in EST-SSR results were selected for further physiological variation investigation. Microstructural examinations revealed no apparent differentiation among the representative strains. However, colony morphology under a range of culture media varied substantially between strains, as did the extracellular enzymatic activity (cellulase, pectinase, protease, and polyphenol oxidase); the data indicate that there are differences in physiological metabolic capacity among A. cristatus strains.

Discussion

Notably, JH1805, B1, and A11 exhibited higher enzymatic activity, indicating their potential application in the production of genetically improved strains. The findings provide valuable insights into species identification, genetic diversity determination, and marker-assisted breeding strategies for A. cristatus.

Current perspective in research and industrial applications of microbial cellulases

The natural interactions between various bacteria, fungi, and other cellulolytic microorganisms destroy lignocellulosic polymers. The efficacy of this process is determined by the combined action of three main enzymes: endoglucanases, exo-glucanases, and β-glucosidase. The enzyme attacks the polymeric structure's β-1,4-linkages during the cellulose breakdown reaction. This mechanism is crucial for the environment as it recycles cellulose in the biosphere. However, there are problems with enzymatic cellulose breakdown, including complex cellulase structure, insufficient degradation efficacy, high production costs, and post-translational alterations, many of which are closely related to certain unidentified cellulase properties. These issues impede the practical use of cellulases. A developing area of research is the application of this similar paradigm for industrial objectives. Cellulase enzyme exhibits greater promise in many critical industries, including biofuel manufacture, textile smoothing and finishing, paper and pulp manufacturing, and farming. However, the study on cellulolytic enzymes must move forward in various directions, including increasing the activity of cellulase as well as designing peptides to give biocatalysts their desired attributes. This manuscript includes an overview of current research on different sources of cellulases, their production, and biochemical characterization.

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.

Bioprospecting of endophytic fungi from medicinal plant Anisomeles indica L. for their diverse role in agricultural and industrial sectors

Endophytes are microorganisms that inhabit various plant parts and cause no damage to the host plants. During the last few years, a number of novel endophytic fungi have been isolated and identified from medicinal plants and were found to be utilized as bio-stimulants and bio fertilizers. In lieu of this, the present study aims to isolate and identify endophytic fungi associated with the leaves of Anisomeles indica L. an important medicinal plant of the Terai-Duars region of West Bengal. A total of ten endophytic fungi were isolated from the leaves of A. indica and five were identified using ITS1/ITS4 sequencing based on their ability for plant growth promotion, secondary metabolite production, and extracellular enzyme production. Endophytic fungal isolates were identified as Colletotrichum yulongense Ai1, Colletotrichum cobbittiense Ai2, Colletotrichum alienum Ai2.1, Colletotrichum cobbittiense Ai3, and Fusarium equiseti. Five isolates tested positive for their plant growth promotion potential, while isolates Ai4. Ai1, Ai2, and Ai2.1 showed significant production of secondary metabolites viz. alkaloids, phenolics, flavonoids, saponins, etc. Isolate Ai2 showed maximum total phenolic concentration (25.98 mg g-1), while isolate Ai4 showed maximum total flavonoid concentration (20.10 mg g-1). Significant results were observed for the production of extracellular enzymes such as cellulases, amylases, laccases, lipases, etc. The isolates significantly influenced the seed germination percentage of tomato seedlings and augmented their growth and development under in vitro assay. The present work comprehensively tested these isolates and ascertained their huge application for the commercial utilization of these isolates both in the agricultural and industrial sectors.

Upstream and Downstream Bioprocessing in Enzyme Technology

The development of biotransformation must integrate upstream and downstream processes. Upstream bioprocessing will influence downstream bioprocessing. It is essential to consider this because downstream processes can constitute the highest cost in bioprocessing. This review comprehensively overviews the most critical aspects of upstream and downstream bioprocessing in enzymatic biocatalysis. The main upstream processes discussed are enzyme production, enzyme immobilization methodologies, solvent selection, and statistical optimization methodologies. The main downstream processes reviewed in this work are biocatalyst recovery and product separation and purification. The correct selection and combination of upstream and downstream methodologies will allow the development of a sustainable and highly productive system.

Microbial cellulase production and its potential application for textile industries

Purpose

The textile industry’s previous chemical use resulted in thousands of practical particulate emissions, such as machine component damage and drainage system blockage, both of which have practical implications. Enzyme-based textile processing is cost-effective, environmentally friendly, non-hazardous, and water-saving. The purpose of this review is to give evidence on the potential activity of microbial cellulase in the textile industry, which is mostly confined to the realm of research.

Methods

This review was progressive by considering peer-reviewed papers linked to microbial cellulase production, and its prospective application for textile industries was appraised and produced to develop this assessment. Articles were divided into two categories based on the results of trustworthy educational journals: methods used to produce the diversity of microorganisms through fermentation processes and such approaches used to produce the diversity of microbes through microbial fermentation. Submerged fermentation (SMF) and solid-state fermentation (SSF) techniques are currently being used to meet industrial demand for microbial cellulase production in the bio textile industry.

Results

Microbial cellulase is vital for increasing day to day due to its no side effect on the environment and human health becoming increasingly important. In conventional textile processing, the gray cloth was subjected to a series of chemical treatments that involved breaking the dye molecule’s amino group with Cl − , which started and accelerated dye(-resistant) bond cracking. A cellulase enzyme is primarily derived from a variety of microbial species found in various ecological settings as a biotextile/bio-based product technology for future needs in industrial applications.

Conclusion

Cellulase has been produced for its advantages in cellulose-based textiles, as well as for quality enhancement and fabric maintenance over traditional approaches. Cellulase’s role in the industry was microbial fermentation processes in textile processing which was chosen as an appropriate and environmentally sound solution for a long and healthy lifestyle.

Solid-State Fermentation of Steam-Exploded Opuntia ficus-indica Cladodes Using Trichoderma reesei CCT-2768 for the Production of Cellulolytic Enzymes

The sustainable development of the drylands, i.e., regions with limited availability of water, depends on the exploitation of the few biomass types that can thrive in such conditions, such as the Opuntia ficus-indica, a plant of the Cactaceae family. In the present study, the cladodes of O. ficus-indica were used as a substrate by the fungus Trichoderma reesei CCT-2768 for the production of cellulolytic enzymes through solid-state fermentation. Firstly, the extraction of the mucilage, soluble components of industrial interest, was evaluated. Temperature, water-to-biomass ratio, and time of mixture were varied using an experimental design and impacted, especially, the pectin removal. Then, the lignocellulosic residue was used for the production of enzymes; the effect of the water activity, biomass pretreatment, mineral supplementation, temperature, and inoculum size on the enzymatic production were investigated using two sets of experimental designs. The steam explosion pretreatment exposed the fiber to the microbial action and boosted the enzyme production, provided that the medium was supplemented with salts. This combination has improved the production of xylanase, CMCase, FPase, and polygalacturonase by 27, 62, 98, and 185%, respectively. The temperature of 35 °C was determined as the optimal for the production of FPase, xylanase, and polygalacturonase, while no effect was observed on the production of CMCase and β-glucosidase. The optimization of the enzymatic production performed in this study can potentially provide a new application for the Opuntia biomass and improve the sustainable development of the drylands.

Lignocellulolytic Biocatalysts: The Main Players Involved in Multiple Biotechnological Processes for Biomass Valorization

Human population growth, industrialization, and globalization have caused several pressures on the planet's natural resources, culminating in the severe climate and environmental crisis which we are facing. Aiming to remedy and mitigate the impact of human activities on the environment, the use of lignocellulolytic enzymes for biofuel production, food, bioremediation, and other various industries, is presented as a more sustainable alternative. These enzymes are characterized as a group of enzymes capable of breaking down lignocellulosic biomass into its different monomer units, making it accessible for bioconversion into various products and applications in the most diverse industries. Among all the organisms that produce lignocellulolytic enzymes, microorganisms are seen as the primary sources for obtaining them. Therefore, this review proposes to discuss the fundamental aspects of the enzymes forming lignocellulolytic systems and the main microorganisms used to obtain them. In addition, different possible industrial applications for these enzymes will be discussed, as well as information about their production modes and considerations about recent advances and future perspectives in research in pursuit of expanding lignocellulolytic enzyme uses at an industrial scale.

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.

Synergistic hydrolysis of filter paper by recombinant cellulase cocktails leveraging a key cellobiase, Cba2, of Cellulomonas biazotea

Cellulomonas biazotea, a Gram-positive cellulolytic bacterium isolated from soil, is capable of producing a complete cellulase complex exhibiting endoglucanase, exoglucanase, and cellobiase activities. Despite the presence of a full complement of all three types of cellulases, samples prepared from both cell lysates and culture media of C. biazotea showed only weak synergistic activities formed among the cellulase components, as reflected by their inefficient performance in filter paper hydrolysis. However, when the five previously characterized recombinant cellobiases of C. biazotea were mixed individually or in different combinations with recombinant enzyme preparations (CenA/Cex) containing an endoglucanase, CenA, and an exoglucanase, Cex, of another Cellulomonas species, C. fimi, the cellulase cocktails exhibited not only much higher but also synergistic activities in filter paper hydrolysis. Among the 5 C. biazotea cellobiases studied, Cba2 was shown to perform 2.8 to 3.8 times better than other homologous isozymes when acting individually with CenA/Cex. More noteworthy is that when Cba2 and Cba4 were added together to the reaction mixture, an even better synergistic effect was achieved. The filter paper activities resulting from Cba2 and Cba4 interacting with CenA/Cex are comparable to those obtained from some commercial fungal cellulase mixtures. To our knowledge, our results represent the first demonstration of synergistic effects on filter paper hydrolysis achieved using recombinant bacterial cellulases.

Production of bioethanol from food waste: Status and perspectives

There is an immediate global requirement for an ingenious strategy for food waste conversion to biofuels in order to replace fossil fuels with renewable resources. Food waste conversion to bioethanol could lead to a sustainable process having the dual advantage of resolving the issue of food waste disposal as well as meeting the energy requirements of the increasing population. Food waste is increasing at the rate of 1.3 billion tonnes per year, considered to be one-third of global food production. According to LCA studies discarding these wastes is detritus to the environment, therefore; it is beneficial to convert the food waste into bioethanol. The CO₂ emission in this process offers zero impact on the environment as it is biogenic. Among several pretreatment strategies, hydrothermal pretreatment could be a better approach for pretreating food waste because it solubilizes organic solids, resulting in an increased recovery of fermentable sugars to produce bioenergy.

Cellulase activity of a novel bacterial strain Arthrobacter woluwensis TDS9: its application on bioconversion of paper mill sludge

Background

Lignocellulosic biomasses produced from agriculture and forest-based industries are the cheapest or negative-cost biomass with a great potential for biotransformation to value-added bioproducts. Paper mill sludge, an important lignocellulosic biomass creates an environmental threat, which requires financial input for disposal. Thus, this study was aimed to isolate a novel bacterial strain capable of degrading cellulosic biomass including paper mill sludge to produce reducing sugar and other value-added bioproducts.

Results

A novel bacterial strain Arthrobacter woluwensis TDS9 isolated from the soil was screened for its cellulolytic activity using carboxymethyl cellulose (CMC) as the sole carbon source. The incubation period, temperature, pH, carbon, and nitrogen sources are the most important factors ruling the CMCase and sugar productions of the strain A. woluwensis TDS9, and an alkaline pH (pH 8.0) led to enhanced sugar production up to 1100.09 μg/mL after 72 h of incubation at 25°C in a medium containing 1.5% CMC and 1.25% beef extract. The optimal conditions for maximum CMCase activity were defined, and the potassium ion boosted the CMCase activity up to 1.06 U/mL when the enzymatic reaction was performed for 30 min at 50°C and pH 8 using CMC as a substrate. Moreover, the strain A. woluwensis TDS9 produced 433.33 μg/mL reducing sugar from 1% pretreated paper mill sludge. Significant alterations in the structural arrangement of cellulosic fiber of paper mill sludge observed under microscope after each step of chemical treatment process helped for loosening the cellulose fibers and increased the saccharification for enzymatic hydrolysis. Endoglucanase IV (33 KDa) and beta-glucosidase II (53 KDa) were identified in crude enzyme based on the zymogram analysis and substrate specificity.

Conclusions

The research has for the first time proved that this A. woluwensis TDS9 strain can efficiently convert cellulose. Therefore, the strain TDS9 could be a potential candidate for cellulase production in an industrial biotransformation process of paper mill sludge to produce reducing sugar. This sugar stream can be further used as a substrate to produce biofuels and other organic acids using another microorganism, which represents a greener alternative to add value to the paper production helping paper mill industries.

Regulation of β-Disaccharide Accumulation by β-Glucosidase Inhibitors to Enhance Cellulase Production in Trichoderma reesei

Trichoderma reesei is a high-yield producer of cellulase for applications in lignocellulosic biomass conversion, but its cellulase production requires induction. A mixture of glucose and β-disaccharide has been demonstrated to achieve high-level cellulase production. However, as inducers, β-disaccharides are prone to be hydrolyzed by β-glucosidase (BGL) during fermentation, therefore β-disaccharides need to be supplemented through feeding to overcome this problem. Here, miglitol, an α-glucosidase inhibitor, was investigated as a BGL inhibitor, and exhibited an IC50 value of 2.93 μg/mL. The cellulase titer was more than two-fold when miglitol was added to the fermentation medium of T. reesei. This method was similar to the prokaryotic expression system using unmetabolized isopropyl-β-D-thiogalactopyranoside (IPTG) as the inducer instead of lactose to continuously induce gene expression. However, cellulase activity was not enhanced with BGL inhibition when lactose or cellulose was used as an inducer, which demonstrated that the transglycosidase activity of BGL is important for the inducible activity of lactose and cellulose. This novel method demonstrates potential in stimulating cellulase production and provides a promising system for T. reesei protein expression.

Identification, characterization and hydrolase producing performance of thermophilic bacteria: geothermal hot springs in the Eastern and Southeastern Anatolia Regions of Turkey

In the last two decades, researchers have increasingly focused on the rich microorganism-based diversity of natural hot spring sources to explore the benefits of thermophiles in industrial and biotechnological fields. Within the scope of this study, a total of 83 thermophilic Bacilli strains were isolated from 7 different geothermal hot springs (at temperatures ranging between 40 and 85 °C) located in the Eastern and Southeastern Anatolia Regions of Turkey. The physiological, morphological, biochemical and molecular properties of the isolates were determined. As a result of the 16S rRNA gene sequence analysis, 5 different species (Bacillus licheniformis, Bacillus sp., Bacillus subtilis, Geobacillus kaustophilus, and Weizmannia coagulans,) were identified. B. licheniformis and B. subtilis were the most frequently encountered species among those obtained from the researched hot spring sources. Phylogenetic analysis was conducted to evaluate the phylogenetic relationships of the isolated species. The results showed that there was no significant difference between the groups and the bacteria in terms of the locations or optimum temperatures of the isolates. The bacterial isolates were screened for amylase, cellulase, lipase and protease hydrolytic enzyme activities. The hydrolytic enzyme production potentials among the isolates were identified in 68 (82%) isolates for amylase, 34 (41%) for cellulase, 69 (83%) for lipase and 73 (88%) for protease. All isolates were found to have at least one or more extracellular enzyme activities. Additionally, it was determined that 27 of the existing isolates (32.8%) were able to produce all of the aforementioned hydrolytic enzymes.

Identifying the negative cooperation between major inhibitors of cellulase activity and minimizing their inhibitory potential during hydrolysis of acid-pretreated corn stover

Soluble compounds produced during the enzymatic hydrolysis of lignocelluloses hampers cellulose conversion. Cellobiose and vanillin most severely inhibited the effect of cellobiohydrolase I. A concentration-dependent negative cooperative effect was found between cellobiose and vanillin. The combined inhibitory effect was about 83.5% of the cellobiose and 88.1% of the vanillin when their concentration was 20 mg/ml. However, the negative synergy could be eliminated by excessive enzyme loading. Differences in their binding sites on the catalytic domain of cellobiohydrolase I lead to negative synergistic inhibition, which should be considered in devising strategies to alleviate this effect. Combined β-glucosidase and PEG addition at an appropriate dose was feasible to balance cost and hydrolytic efficiency. To achieve efficient hydrolysis, especially at high solid concentrations, it is important to understand the synergistic inhibition between these inhibitors.

Thalassobacillus, a genus of extreme to moderate environmental halophiles with biotechnological potential

Thalassobacillus is a moderately halophilic genus that has been isolated from several sites worldwide, such as hypersaline lakes, saline soils, salt flats, and volcanic mud. Halophilic bacteria have provided functional stable biomolecules in harsh conditions for industrial purposes. Despite its potential biotechnological applications, Thalassobacillus has not been fully characterized yet. This review describes the Thalassobacillus genus, with the few species reported, pointing out its possible applications in enzymes (amylases, cellulases, xylanases, and others), biosurfactants, bioactive compounds, biofuels production, bioremediation, and plant growth promotion. The Thalassobacillus genus represents a little-explored biological resource but with a high potential.

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.