Concomitant production of cellulase and xylanase by thermophilic mould Sporotrichum thermophile in solid state fermentation and their applicability in bread making

Advances of microbial xylanases in the application of flour industries: A comprehensive review

Microbial xylanase has a wide range of applications, and many researchers favoring its utilization as an alternative to improve flour products. Wheat flour is the main raw material of flour products, although the content of arabinoxylan is not high in flour products, but it has a great influence on the quality of flour products, microbial xylanase can act on wheat arabinoxylan, so as to play the role of flour product improvement. This review carries out a description of the research progress on the application of xylanases in flour products in terms of xylanase properties, different families of xylanases and improvement mechanisms of xylanases in flour products. According to the properties of various microbial sources of xylanases, the suitable xylanase can be added to flour products, and the effect of xylanase towards wheat arabinoxylan in flour can be used to improve the quality of flour products. The molecular modification based on the properties of xylanase and the crystal structure of different families of xylanase and their substrate specificity toward wheat arabinoxylan are discussed. The article reviews the information about microbial xylanases in order to achieve better results in flour products and to provide a theoretical basis for their industrial application.

Probiotics in the Sourdough Bread Fermentation: Current Status

Sourdough fermentation is an ancient technique to ferment cereal flour that improves bread quality, bringing nutritional and health benefits. The fermented dough has a complex microbiome composed mainly of lactic acid bacteria and yeasts. During fermentation, the production of metabolites and chemical reactions occur, giving the product unique characteristics and a high sensory quality. Mastery of fermentation allows adjustment of gluten levels, delaying starch digestibility, and increasing the bio-accessibility of vitamins and minerals. This review focuses on the main steps of sourdough fermentation, the microorganisms involved, and advances in bread production with functional properties. The impact of probiotics on human health, the metabolites produced, and the main microbial enzymes used in the bakery industry are also discussed.

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.

Thermostable cellulose saccharifying microbial enzymes: Characteristics, recent advances and biotechnological applications

Cellulases play a promising role in the bioconversion of renewable lignocellulosic biomass into fermentable sugars which are subsequently fermented to biofuels and other value-added chemicals. Besides biofuel industries, they are also in huge demand in textile, detergent, and paper and pulp industries. Low titres of cellulase production and processing are the main issues that contribute to high enzyme cost. The success of ethanol-based biorefinery depends on high production titres and the catalytic efficiency of cellulases functional at elevated temperatures with acid/alkali tolerance and the low cost. In view of their wider application in various industrial processes, stable cellulases that are active at elevated temperatures in the acidic-alkaline pH ranges, and organic solvents and salt tolerance would be useful. This review provides a recent update on the advances made in thermostable cellulases. Developments in their sources, characteristics and mechanisms are updated. Various methods such as rational design, directed evolution, synthetic & system biology and immobilization techniques adopted in evolving cellulases with ameliorated thermostability and characteristics are also discussed. The wide range of applications of thermostable cellulases in various industrial sectors is described.

Biochemical properties of cellulolytic and xylanolytic enzymes from Sporotrichum thermophile and their utility in bioethanol production using rice straw

Production of cellulolytic and xylanolytic enzymes by Sporotrichum thermophile was enhanced using response surface methodology in solid-state fermentation (SSF) using wheat straw and cotton oil cake. Cellulolytic and xylanolytic enzymes were partially purified by ammonium sulfate precipitation followed by ion exchange and gel filtration chromatographic techniques. Xylanase of S. thermophile is neutral xylanase displaying optimal activity at 60 °C with K_m and V_max values of 0.2 mg/mL and 238.05 µmole/min, respectively. All cellulases produced by the thermophilic mold showed optimal activity at pH 5.0 and 60 °C with K_m values of 0.312 mg/mL, 0.113 mg/mL, and 0.285 mM for carboxymethyl cellulase (CMCase), filter paper cellulase (FPase), and β-glucosidase, respectively and while V_max values were 181.81, 138.88, and 66.67 µmole/min, respectively. The presence of various metal ions (Ca²⁺ and Co²⁺), chemical reagent (glutaraldehyde), and surfactants (Tween 80 and Triton X-100) significantly improved the activities of all enzymes. All the enzymes showed high storage stability under low temperature (-20 and 4 °C) conditions. Cellulolytic and xylanolytic enzymes resulted in enhanced liberation of reducing sugars (356.34 mg/g) by hydrolyzing both cellulosic and hemicellulosic fractions of ammonia-pretreated rice straw as compared to other pretreatment methods used in the study. Fermentation of enzymatic hydrolysate resulted in the formation of 28.88 and 27.18 g/L of bioethanol in separate hydrolysis and fermentation (SHF) process by Saccharomyces cerevisiae and Pichia stipitis, respectively. Therefore, cellulolytic and xylanolytic enzymes of S. thermophile exhibited ideal properties of biocatalysts useful in the saccharification of cellulosic and hemicellulosic fractions of rice straw for the production of bioethanol.

Biochemical characterization and enhanced production of endoxylanase from thermophilic mould Myceliophthora thermophila

Endoxylanase production from M. thermophila BJTLRMDU3 using rice straw was enhanced to 2.53-fold after optimization in solid state fermentation (SSF). Endoxylanase was purified to homogeneity employing ammonium sulfate precipitation followed by gel filtration chromatography and had a molecular mass of ~ 25 kDa estimated by SDS-PAGE. Optimal endoxylanase activity was recorded at pH 5.0 and 60 °C. Purified enzyme showed complete tolerance to n-hexane, but activity was slightly inhibited by other organic solvents. Among surfactants, Tweens (20, 60, and 80) and Triton X 100 slightly enhanced the enzyme activity. The V_max and K_m values for purified endoxylanase were 6.29 µmol/min/mg protein and 5.4 mg/ml, respectively. Endoxylanase released 79.08 and 42.95% higher reducing sugars and soluble proteins, respectively, which control after 48 h at 60 °C from poultry feed. Synergistic effect of endoxylanase (100 U/g) and phytase (15 U/g) on poultry feed released higher amount of reducing sugars (58.58 mg/feed), soluble proteins (42.48 mg/g feed), and inorganic phosphate (28.34 mg/feed) in contrast to control having 23.55, 16.98, and 10.46 mg/feed of reducing sugars, soluble proteins, and inorganic phosphate, respectively, at 60 °C supplemented with endoxylanase only.

Biochemical and Biotechnological Studies on Xylanase and β‐xylosidase Enzymes Produced by Trichoderma viride Under Solid State Fermentation

The current study concerns with enhancement of xylanase and β-xylosidase activities from lignocellulosic materials by soil derived fungi Trichoderma viride under solid state fermentation (SSF). Xylanase and β-xylosidase activities were found to affected by variety of factors. In this study, some agricultural wastes were selected and used as sources for carbon. Sugar beet pulp (SBP) was at the forefront of these types. Also, various sources for nitrogen were selected to determine the best one. Yeast extract was the best organic source. Maximum xylanase activity took place by using inoculum size 1.8 × 105 spores / ml at 30°C when the pH was 5.5 for eight days of incubation with the addition of 0.1 % of Tween 40. Moreover, spores of Trichoderma viride were irradiated with gamma–rays. The maximum activity was observed upon using 0.7 kilo-gray (kGy). Furthermore, mixed cultures of Trichoderma viride and Penicillium janthenellum (wt / wt) were enhanced xylanase degrading capability. From another standpoint, ammonium sulphate and gel filtration chromatography were the best methods for xylanase purification. Characterizations of the purified enzyme were also selected and studied. It was found that, β-xylosidase enzyme exhibited its maximum activity and stability when the pH was 6 at 40°C by the addition of CaCl2 metal ion. On the other hand, total protein contents and volatile constituents of Trichoderma viride and Penicillium janthenellum were separated and investigated using high performance liquid chromatography (HPLC) and gas chromatography/mass spectrometry (GC/MS) techniques. It was found that, total protein contents for Trichoderma viride and Penicillium janthenellum were represented by fifteen and sixteen amino acids respectively. Also,29 compounds of the total volatile compounds for both Trichoderma viride and Penicillium janthenellum were identified. On the practical and applied field, crude enzyme was a good analyzer for agricultural residues as well showed antifungal and antibacterial effects.

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.

Preparation and Characterization of Cinnamomum Essential Oil–Chitosan Nanocomposites: Physical, Structural, and Antioxidant Activities

In this study, different amounts of cinnamomum essential oil (CEO) were encapsulated in chitosan nanoparticles (NPs) (CS-NPs) through oil-in-water emulsification and ionic gelation. An ultraviolet-visible spectrophotometer, Fourier-transform infrared spectroscopy, synchronous thermal analysis, and X-ray diffraction were employed to analyze the CEO encapsulation. As observed by field-emission scanning electron microscopy, NP size analysis and zeta potential, the prepared CS-NPs, containing CEO (CS-CEO), were spherical with uniformly distributed sizes (diameters: 190–340 nm). The ranges of encapsulation efficiency (EE) and loading capacity (LC) were 4.6–32.9% and 0.9–10.4%, with variations in the starting weight ratio of CEO to CS from 0.11 to 0.53 (w/w). It was also found that the antioxidant activity of the CS-NPs loaded with CEO increased as the EE increased. The active ingredients of the CEO were prevented from being volatilized, significantly improving the chemical stability. The antioxidant activity of CS-CEO was higher than that of the free CEO. These results indicate the promising potential of CS-CEO as an antioxidant for food processing, and packaging applications.

Isolation of Thermostable Lignocellulosic Bacteria From Chicken Manure Compost and a M42 Family Endocellulase Cloning From Geobacillus thermodenitrificans Y7

The composting ecosystem provides a potential resource for finding new microorganisms with the capability for cellulose degradation. In the present study, Congo red method was used for the isolating of thermostable lignocellulose-degrading bacteria from chicken manure compost. A thermophilic strain named as Geobacillus thermodenitrificans Y7 with acid-resident property was successfully isolated and employed to degrade raw switchgrass at 60°C for 5 days, which resulted in the final degradation rates of cellulose, xylan, and acid-insoluble lignin as 18.64, 12.96, and 17.21%, respectively. In addition, GC-MS analysis about aromatic degradation affirm the degradation of lignin by G. thermodenitrificans Y7. Moreover, an endocellulase gene belong to M42 family was successfully cloned from G. thermodenitrificans Y7 and expressed in Escherichia coli BL21. Recombinant enzyme Cel-9 was purified by Ni-NTA column based the His-tag, and the molecular weight determined as 40.4 kDa by SDA-PAGE. The characterization of the enzyme Cel-9 indicated that the maximum enzyme activity was realized at 50°C and pH 8.6 and, Mn2+ could greatly improve the CMCase enzyme activity of Cel-9 at 10 mM, which was followed by Fe2+ and Co2+. Besides, it also found that the β-1,3-1,4, β-1,3, β-1,4, and β-1,6 glucan linkages all could be hydrolyzed by enzyme Cel-9. Finally, during the application of enzyme Cel-9 to switchgrass, the saccharification rates achieved to 1.81 ± 0.04% and 2.65 ± 0.03% for 50 and 100% crude enzyme, respectively. All these results indicated that both the strain G. thermodenitrificans Y7 and the recombinant endocellulase Cel-9 have the potential to be applied to the biomass industry.

Enhanced production of bacterial xylanase and its utility in saccharification of sugarcane bagasse

An investigation was carried out using sugarcane bagasse as the agricultural residue to study the optimization of xylanase production by solid-state fermentation. Maximum xylanase production (20.35 U/g substrate) was achieved by Bacillus substilis subsp. subtilis JJBS250 using 'one variable at a time approach' at pH 7.0, 40 °C after 48 h. After statistical optimization by response surface methodology (RSM) there was 4.82-fold improvement in xylanase production (98.16 U/g substrate). Further optimization of untreated and sodium carbonate pretreated sugarcane bagasse enzymatic hydrolysis was carried out using both bacterial (Bacillus substilis subsp. subtilis JJBS250) and fungal (Myceliophthora thermophila BJTLRMDU3) xylanases that showed high amount of reducing sugar liberation from untreated sugarcane bagasse (124.24 mg/g substrate) as compared to pretreated (76.23 mg/g substrate) biomass. Furthermore, biophysical characterization of untreated and sodium carbonate pretreated sugarcane bagasse using Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM), revealed the structural changes in the pretreated biomass.

Production, characteristics, and biotechnological applications of microbial xylanases

Microbial xylanases have gathered great attention due to their biotechnological potential at industrial scale for many processes. A variety of lignocellulosic materials, such as sugarcane bagasse, rice straw, rice bran, wheat straw, wheat bran, corn cob, and ragi bran, are used for xylanase production which also solved the great issue of solid waste management. Both solid-state and submerged fermentation have been used for xylanase production controlled by various physical and nutritional parameters. Majority of xylanases have optimum pH in the range of 4.0-9.0 with optimum temperature at 30-60 °C. For biochemical, molecular studies and also for successful application in industries, purification and characterization of xylanase have been carried out using various appropriate techniques. Cloning and genetic engineering are used for commercial-level production of xylanase, to meet specific economic viability and industrial needs. Microbial xylanases are used in various biotechnological applications like biofuel production, pulp and paper industry, baking and brewing industry, food and feed industry, and deinking of waste paper. This review describes production, characteristics, and biotechnological applications of microbial xylanases.

Enhanced endoxylanase production by Myceliophthora thermophila with applicability in saccharification of agricultural substrates

The production of enzymes by solid-state fermentation is an interesting process and currently used worldwide as it can be carried out in solid matrix in absence of free water. In present study, Myceliophthora thermophila BJTLRMDU3 produced high titres of endoxylanase (890.55 U/g DR, dry residue) using 5 g rice straw at pH 7.0 and at 45 °C with 1:7 (w/v) solid-to-moisture ratio with inoculum rate of 12 × 10⁶ spores/ml after 4 days in solid-state fermentation. High enzyme titre was produced after moistening the rice straw with solution containing ammonium sulphate (0.4%), K₂HPO₄ (1.0%), MgSO₄·7H₂O (0.3%), FeSO₄·7H₂O (0.03%) and CaCl₂ (0.03%). Addition of sucrose (2% w/v) and ammonium nitrate (2% w/v) further enhanced the endoxylanase production. A high endoxylanase production was achieved at water activity (a _W) of 0.95 (1639.80 U/g DR) that declined drastically below this value. Among different surfactants, Tween 20 (3% v/v) enhanced the secretion of endoxylanase (2047.91 U/g DR). Furthermore, on optimization of K₂HPO₄ concentration, it was found that 0.5% K₂HPO₄ improved (2191.28 U/g DR) endoxylanase production and overall 4.35-folds increase in production of endoxylanase was achieved after optimization of culture conditions. The enzyme has potential to liberate monomeric (xylose) as well as oligomeric (xylotiose, xylotetrose, and xylopantose) sugars from xylan. On saccharification of rice straw and corncob with endoxylanase, maximum yield of reducing sugars was 135.61 and 132.61 mg/g of substrate recorded after 48, and 36 h, respectively.

It Is the Mix that Matters: Substrate-Specific Enzyme Production from Filamentous Fungi and Bacteria Through Solid-State Fermentation

Fungi have a diverse spectrum of extracellular enzymes. In nature, extracellular enzymes primarily serve to procure nutrients for the survival and growth of the fungi. Complex polymers such as lignocellulose and starch as well as proteins and fats are broken down into their basic building blocks by extracellular enzymes such as amylases, proteases, lipases, xylanases, laccases, and many more.The abilities of these enzymes are made use of in diverse areas of industry, including food technology, textiles, and pharmaceuticals, and they have become indispensable for today's technology. Enzyme production is usually carried out using submerged fermentation (SmF). However, as part of the search for more sustainable uses of raw materials, solid-state fermentation (SSF) has become the focus of research.The rate of enzyme formation depends on different factors, for example, microorganism, temperature, or oxygen supply. However, one of the most important factors in enzyme production is the choice of substrate, which varies depending on the desired target enzyme. Substrates with proven effectiveness include wheat bran and straw, but unusual agricultural residues such as forage cactus pears and orange peels have surprisingly positive effects on enzyme formation as well.This review gives an overview of various technically relevant enzymes produced by filamentous fungi and suitable substrates for the production of the enzymes by SSF. Graphical Abstract.