Characterization of a recombinant alkaline thermostable β-mannanase and its application in eco-friendly ramie degumming

The response surface optimization of β-mannanase produced by Weissella cibaria F1 and its potential in juice clarification

A β-mannanase-producing lactic acid bacteria (LAB) was identified as Weissella cibaria F1 according to physiological and biochemical properties, morphological observations, partial sequence of 16S rRNA gene and API 50 CHL test. In order to improve the yield of β-mannanase, the response surface methodology (RSM) was originally used to optimize the fermentation conditions. The optimization results showed that when the konjac powder, glucose, and initial pH were 9.46 g/L, 14.47 g/L and 5.67, respectively, the β-mannanase activity increased to 38.81 ± 0.33 U/mL, which was 1.33 times compared to initial yield (29.28 ± 0.26 U/mL). This result was also supported by larger clearance on the konjac powder-MRS agar plate through Congo Red dyeing. The W. cibaria F1 β-mannanase could improve the clarity of five fruits juice, i.e., apple, orange, peach, persimmon and blue honeysuckle. Among these, peach juice was the most obvious, clarity increasing by 12.8%. These results collectively indicated that W. cibaria F1 β-mannanase had an applicable potential in food-level fields.

Bacterial strain for bast fiber crops degumming and its bio-degumming technique

The research and development of bio-degumming technology is under a slow progress due to the shortage of proper efficient bacterial strains and processes. A degumming bacterial strain-Pectobacterium wasabiae (PW)-with broad-spectrum degumming abilities was screened out in this study. After the fermentation for 12 h, the residual gum contents of kenaf bast, ramie bast, hemp bast, flax bast, and Apocynum venetum bast were all lower than 15%. This bacterial strain could realize the simultaneous extracellular secretion of pectinase, mannase, and xylanase with the maximum enzyme activity levels of 130.25, 157.58, and 115.24 U/mL, respectively. The optimal degumming conditions of this bacterial strain were as follows: degumming time of 12 h, bath ratio of 1:10, temperature of 33 °C, and inoculum size of 2%. After the bio-degumming through this bacterial strain, the COD in wastewater was below 4000 mg/L, which was over 60% lower than that in boiling-off wastewater generated by chemical degumming. This technology achieves higher efficiency, higher quality, and lower pollution.

High-level expression of a β-mannanase (manB) in Pichia pastoris GS115 for mannose production with Penicillium brevicompactum fermentation pretreatment of soybean meal

An endo-1,4-β-mannanase gene (manB) from a Bacillus pumilus Nsic-2 grown in a stinky tofu emulsion was cloned and expressed in Pichia pastoris GS115. After characterized, the endo-1,4-β-mannanase (manB) show maximum activity at pH 6.0 and 50 °C with LBG as substrate and perform high stability at a range of pH 6-8. After applying for a shake flask fermentation, the specific activity of manB reached 3462 U/mg. To produce mannose, the soybean meal (SBM) was pretreated by biological fermentation for 11 days with Penicillium brevicompactum, and then hydrolyzed by manB. As a result, mannose yield reached 3.58 g per 1 kg SBM which indicated that 0.358% SBM was converted into mannose after hydrolyzation, and mean a total 20% mannan of SBM converting into mannose, while the control group demonstrated only 1.78% conversion. An effective β-mannanase for the bioconversion of mannan-rich biomasses and an efficient method to produce mannose with soybean meal were introduced.

Molecular advancements on over-expression, stability and catalytic aspects of endo-β-mannanases

The hydrolysis of mannans by endo-β-mannanases continues to gather significance as exemplified by its commercial applications in food, feed, and a rekindled interest in biorefineries. The present review provides a comprehensive account of fundamental research and fascinating insights in the field of endo-β-mannanase engineering in order to improve over-expression and to decipher molecular determinants governing activity-stability during harsh conditions, substrate recognition, polysaccharide specificity, endo/exo mode of action and multi-functional activities in the modular polypeptide. In-depth analysis of the available literature has also been made on rational and directed evolution approaches, which have translated native endo-β-mannanases into superior biocatalysts for satisfying industrial requirements.

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.