Understanding β-mannanase from Streptomyces sp. CS147 and its potential application in lignocellulose based biorefining

Manno-Oligosaccharide Production from Biomass Hydrolysis by Using Endo-1,4-β-Mannanase (ManNj6-379) from Nonomuraea jabiensis ID06-379

A novel endo-β-1,4-mannanase gene was cloned from a novel actinomycetes, Nonomuraea jabiensis ID06-379, isolated from soil, overexpressed as an extracellular protein (47.8 kDa) in Streptomyces lividans 1326. This new endo-1,4-β-mannanase gene (manNj6-379) is encoded by 445-amino acids. The ManNj6-379 consists of a 28-residue signal peptide and a carbohydrate-binding module of family 2 belonging to the glycoside hydrolase (GH) family 5, with 59–77% identity to GH5 mannan endo-1,4-β-mannanase. The recombinant ManNj6-379 displayed an optimal pH of 6.5 with pH stability ranging between 5.5 and 7.0 and was stable for 120 min at 50 °C and lower temperatures. The optimal temperature for activity was 70 °C. An enzymatic hydrolysis assay revealed that ManNj6-379 could hydrolyze commercial β-mannan and biomass containing mannan.

Molecular and biochemical characterizations of a new cold-active and mildly alkaline β-Mannanase from Verrucomicrobiae DG1235

Mannanases catalyze the cleavage of β-1,4-mannosidic linkages in mannans and have various applications in different biotechnological industries. In this study, a new β-mannanase from Verrucomicrobiae DG1235 (ManDG1235) was biochemically characterized and its enzymatic properties were revealed. Amino acid alignment indicated that ManDG1235 belonged to glycoside hydrolase family 26 and shared a low amino acid sequence identity to reported β-mannanases (up to 50% for CjMan26C from Cellvibrio japonicus). ManDG1235 was expressed in Escherichia coli. Purified ManDG1235 (rManDG1235) exhibited the typical properties of cold-active enzymes, including high activity at low temperature (optimal at 20 °C) and thermal instability. The maximum activity of rManDG1235 was achieved at pH 8, suggesting that it is a mildly alkaline β-mannanase. rManDG1235 was able to hydrolyze a variety of mannan substrates and was active toward certain types of glucans. A structural model that was built by homology modeling suggested that ManDG1235 had four mannose-binding subsites which were symmetrically arranged in the active-site cleft. A long loop linking β2 and α2 as in CjMan26C creates a steric border in the glycone region of active-site cleft which probably leads to the exo-acting feature of ManDG1235, for specifically cleaving mannobiose from the non-reducing end of the substrate.

Applications of Microbial β-Mannanases

Mannans are main components of hemicellulosic fraction of softwoods and they are present widely in plant tissues. β-mannanases are the major mannan-degrading enzymes and are produced by different plants, animals, actinomycetes, fungi, and bacteria. These enzymes can function under conditions of wide range of pH and temperature. Applications of β-mannanases have therefore, been found in different industries such as animal feed, food, biorefinery, textile, detergent, and paper and pulp. This review summarizes the most recent studies reported on potential applications of β-mannanases and bioengineering of β-mannanases to modify and optimize their key catalytic properties to cater to growing demands of commercial sectors.

β-Mannanase Production Using Coffee Industry Waste for Application in Soluble Coffee Processing

Soluble coffee offers the combined benefits of high added value and practicality for its consumers. The hydrolysis of coffee polysaccharides by the biochemical route, using enzymes, is an eco-friendly and sustainable way to improve the quality of this product, while contributing to the implementation of industrial processes that have lower energy requirements and can reduce environmental impacts. This work describes the production of hydrolytic enzymes by solid-state fermentation (SSF), cultivating filamentous fungi on waste from the coffee industry, followed by their application in the hydrolysis of waste coffee polysaccharides from soluble coffee processing. Different substrate compositions were studied, an ideal microorganism was selected, and the fermentation conditions were optimized. Cultivations for enzymes production were carried out in flasks and in a packed-bed bioreactor. Higher enzyme yield was achieved in the bioreactor, due to better aeration of the substrate. The best β-mannanase production results were found for a substrate composed of a mixture of coffee waste and wheat bran (1:1 w/w), using Aspergillus niger F12. The enzymatic extract proved to be very stable for 24 h, at 50 °C, and was able to hydrolyze a considerable amount of the carbohydrates in the coffee. The addition of a commercial cellulase cocktail to the crude extract increased the hydrolysis yield by 56%. The production of β-mannanase by SSF and its application in the hydrolysis of coffee polysaccharides showed promise for improving soluble coffee processing, offering an attractive way to assist in closing the loops in the coffee industry and creating a circular economy.

Production of Novel Polygalacturonase from Bacillus paralicheniformis CBS32 and Application to Depolymerization of Ramie Fiber

Polygalacturonase (EC. 3.2.1.15) is an enzyme that hydrolyzes the alpha-1,4 glycosidic bonds between galacturonic acid. In this study, an alkaline polygalacturonase producer Bacillus paralicheniformis CBS32 was isolated from kimchi (conventional Korean fermented food). The 16S rRNA sequence analysis of the isolated strain revealed that it was 99.92% identical to B. paralicheniformis KJ 16LBMN01000156. The polygalacturonase from B. paralicheniformis CBS32 was named PN32, and the purified PN32 showed a 16.8% yield and a 33-fold purity compared to the crude broth. The molecular mass, 110 kDa, was determined by SDS-PAGE, and the active band was confirmed by zymography analysis. The N-terminal amino acid sequence residues of PN32 were determined to be Gly–Val–Lys–Glu–Val–X–Gln–Thr–Phe. In the sequence comparison, PN32 was suggested as a novel polygalacturonase, since the sequence was not matched with the previous reports. In an application study, enzymatic depolymerization of ramie was performed for fiber degumming, and the result showed that the PN32 had a 28% higher depolymerization compared to the commercial pectinase. Overall, based on the results, PN32 has high potential for industrial applications.

Enhanced In-Vitro Hemozoin Polymerization by Optimized Process using Histidine-Rich Protein II (HRPII)

Conductive biopolymers, an important class of functional materials, have received attention in various fields because of their unique electrical, optical, and physical properties. In this study, the polymerization of heme into hemozoin was carried out in an in vitro system by the newly developed heme polymerase (histidine-rich protein 2 (HRP-II)). The HRP-II was produced by recombinant E. coli BL21 from the Plasmodium falciparum gene. To improve the hemozoin production, the reaction conditions on the polymerization were investigated and the maximum production was achieved after about 790 μM at 34 °C with 200 rpm for 24 h. As a result, the production was improved about two-fold according to the stepwise optimization in an in vitro system. The produced hemozoin was qualitatively analyzed using the Fourier transform infrared (FTIR) spectroscopy, energy dispersive X-ray spectroscopy (EDS), and scanning electron microscopy (SEM). Finally, it was confirmed that the enzymatically polymerized hemozoin had similar physical properties to chemically synthesized hemozoin. These results could represent a significant potential for nano-biotechnology applications, and also provide guidance in research related to hemozoin utilization.

The response surface optimization of β-mannanase produced by Lactobacillus casei HDS-01 and its potential in juice clarification

Lactic acid bacteria (LAB) is an ideal mannanase source due to the bio-safety guarantee. LAB can heterogeneously express β-mannanase or be directly used as β-mannanase-producing strains. This research originally optimized the fermentation condition for β-mannanase produced by Lactobacillus casei HDS-01. The applicable potential of the crude enzyme in juice clarification was investigated. Two-factorial design screened out three factors, i.e., fermentation time (p = 0.0001), glucose (p = 0.0013), and initial pH (p = 0.0167), which significantly affected L. casei HDS-01 β-mannanase activity. Under the predicted conditions resulting from the central composite design (CCD), i.e., fermentation time 18.23 hr, glucose 12.65 g L^-1, initial pH 5.18, the model reached maximal β-mannanase activity of 81.40 U mL^-1. This model was validated by conducting six repeated experiments and subsequent t-test (p = 0.6308). RSM optimization obtained a 1.33-fold increase in β-mannanase activity. This increase could also be qualitatively detected by larger clearance zone on konjac powder-MRS agar through Congo Red dyeing. The yield and clarity of crude β-mannanase-treated juices from orange, apple, and pear were significantly higher than controls without enzyme treatment. This study conferred a relatively high β-mannanase-producing LAB strain with a high bio-safety level and easy and economical use in juice clarification as well as other food-level fields.

Alkaline Active Hemicellulases

Xylan and mannan are the two most abundant hemicelluloses, and enzymes that modify these polysaccharides are prominent hemicellulases with immense biotechnological importance. Among these enzymes, xylanases and mannanases which play the vital role in the hydrolysis of xylan and mannan, respectively, attracted a great deal of interest. These hemicellulases have got applications in food, feed, bioethanol, pulp and paper, chemical, and beverage producing industries as well as in biorefineries and environmental biotechnology. The great majority of the enzymes used in these applications are optimally active in mildly acidic to neutral range. However, in recent years, alkaline active enzymes have also become increasingly important. This is mainly due to some benefits of utilizing alkaline active hemicellulases over that of neutral or acid active enzymes. One of the advantages is that the alkaline active enzymes are most suitable to applications that require high pH such as Kraft pulp delignification, detergent formulation, and cotton bioscouring. The other benefit is related to the better solubility of hemicelluloses at high pH. Since the efficiency of enzymatic hydrolysis is often positively correlated to substrate solubility, the hydrolysis of hemicelluloses can be more efficient if performed at high pH. High pH hydrolysis requires the use of alkaline active enzymes. Moreover, alkaline extraction is the most common hemicellulose extraction method, and direct hydrolysis of the alkali-extracted hemicellulose could be of great interest in the valorization of hemicellulose. Direct hydrolysis avoids the time-consuming extensive washing, and neutralization processes required if non-alkaline active enzymes are opted to be used. Furthermore, most alkaline active enzymes are relatively active in a wide range of pH, and at least some of them are significantly or even optimally active in slightly acidic to neutral pH range. Such enzymes can be eligible for non-alkaline applications such as in feed, food, and beverage industries.This chapter largely focuses on the most important alkaline active hemicellulases, endo-β-1,4-xylanases and β-mannanases. It summarizes the relevant catalytic properties, structural features, as well as the real and potential applications of these remarkable hemicellulases in textile, paper and pulp, detergent, feed, food, and prebiotic producing industries. In addition, the chapter depicts the role of these extremozymes in valorization of hemicelluloses to platform chemicals and alike in biorefineries. It also reviews hemicelluloses and discusses their biotechnological importance.