Effect of the thermostable xylanase B (XynB) from Thermotoga maritima on the quality of frozen partially baked bread

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.

Marine enzymes: Classification and application in various industries

Oceans are regarded as a plentiful and sustainable source of biological compounds. Enzymes are a group of marine biomaterials that have recently drawn more attention because they are produced in harsh environmental conditions such as high salinity, extensive pH, a wide temperature range, and high pressure. Hence, marine-derived enzymes are capable of exhibiting remarkable properties due to their unique composition. In this review, we overviewed and discussed characteristics of marine enzymes as well as the sources of marine enzymes, ranging from primitive organisms to vertebrates, and presented the importance, advantages, and challenges of using marine enzymes with a summary of their applications in a variety of industries. Current biotechnological advancements need the study of novel marine enzymes that could be applied in a variety of ways. Resources of marine enzyme can benefit greatly for biotechnological applications duo to their biocompatible, ecofriendly and high effectiveness. It is beneficial to use the unique characteristics offered by marine enzymes to either develop new processes and products or improve existing ones. As a result, marine-derived enzymes have promising potential and are an excellent candidate for a variety of biotechnology applications and a future rise in the use of marine enzymes is to be anticipated.

Heterologous expression and biochemical characterization of a cold-active lipase from Rhizopus microsporus suitable for oleate synthesis and bread making

OBJECTIVES

Cold-active lipases which show high specific activity at low temperatures are attractive in industrial applications in terms of product stability and energy saving. We aimed to identify novel cold-active lipase suitable for oleates synthesis and bread making.

RESULTS

A novel lipase gene (RmLipA) from Rhizopus microsporus was cloned and heterologously expressed in Pichia pastoris. The encoding sequence displayed 75% identity to the lipase from R. niveus. The highest extracellular lipase activity of 7931 U/mL was achieved in a 5-L fermentation. The recombinant enzyme (RmLipA) was optimally active at pH 8.0 and 20-25 °C, respectively, and stable over a wide pH range of 2.0-11.0. The enzyme was a cold-active lipase, exhibiting > 80% of its maximal activity at 0 °C. RmLipA was a sn-1,3 regioselective lipase, and preferred to hydrolyze pNP esters and triglycerides with relatively long chain fatty acids. RmLipA synthesized various oleates using oleic acid and different alcohols as substrates (> 95%). Moreover, it significantly improved the quality of bread by increasing its specific volume (21.7%) and decreasing its crumb firmness (28.6%).

CONCLUSIONS

A novel cold-active lipase gene from R. microsporus was identified, and its application potentials were evaluated. RmLipA should be a potential candidate in oleates synthesis and bread making industries.

Evaluation of texture, retrogradation enthalpy, water mobility, and anti-staling effects of enzymes and hydrocolloids in potato steamed bread

The functionalities of hydrocolloids and enzymes in texture, retrogradation enthalpy, water mobility and distribution, and anti-staling effects of potato steamed bread stored for 0, 24, and 48 h at 25 °C were investigated. Four kinds of hydrocolloids, including carrageenan, xanthan gum, arabic gum, sodium alginate, and one kind of enzyme (xylanase) showed little effects on the hardness reduction and springiness retention of potato steamed bread during storage, while the presence of α-amylase and lipase could slow down its staling rate. Potato steamed bread with combination of α-amylase (20 mg/kg) and lipase (40 mg/kg) exhibited the lowest hardness, with a significant reduction of 44.20%, besides improving the specific volume, L*, and overall acceptability in sensory evaluation. The addition of α-amylase and lipase could decrease the retrogradation enthalpy and bound water, and increase the mobility of mobile water. These findings shed efficient methods to retard staling of potato steamed bread.

Effects of Combined α-Amylase and Endo-Xylanase Treatments on the Properties of Fresh and Frozen Doughs and Final Breads

Frozen bread doughs usually exhibit less bread volume and poor texture due to dough weakening as well as reduced yeast viability. The objectives of this study were to improve the textural properties of frozen bread dough by applying carbohydrate-active enzymes, α-amylase and endo-xylanase. Each enzyme was applied to dough formulation at 20 (748 and 3.5 units, respectively) and 100 ppm levels of flour, and their combined treatments were also applied. Enzyme-treated doughs were kept frozen at -20 °C for 2 weeks, and then baked following the official American Association of Cereal Chemists (AACC) method. A texture profile analysis of oven-baked breads was performed at 25 °C after a 5-day storage period. α-Amylase treatment at a 100 ppm level increased the specific bread volume by 24.5% and 21.9% when compared to untreated fresh and frozen bread doughs, respectively, and decreased crumb hardness by 63.4% and 58.3%; endo-xylanase (100 ppm) also decreased crumb hardness by 56.9% and 26.9%. The combined use of α-amylase and endo-xylanase retarded bread hardening synergistically after a 5-day storage period.

The Effects of Amyloglucosidase, Glucose Oxidase and Hemicellulase Utilization on the Rheological Behaviour of Dough and Quality Characteristics of Bread

Wheat flour, whole wheat flour, 25 and 50 % rye flour substituted wheat flour blends, 15 and 30 % wheat bran substituted wheat flour blends were supplemented with amyloglucosidase (at 0.000875 and 0.001 %), glucose oxidase (at 0.0003 and 0.001 %) and hemicellulase (at 0.001 and 0.005 %). The effects of enzymes on the extensographic properties of dough and quality characteristics of bread (specific volume, baking loss percentage and final moisture content) were studied. The interaction between type of flour/blend, type of enzyme and dosage of enzyme affected resistance to extension, extensibility and ratio of resistance to extensibility of doughs significantly. The interactions between type of flour/blend, type of enzyme and dosage of enzyme affected specific volume, baking loss percentage and final moisture content of breads significantly. The findings in this study indicated that enzymes can exhibit unexpected effects on dough and bread properties depending on type of flour and dosage of enzyme.

Bread Staling: Updating the View

Staling of bread is cause of significant product waste in the world. We reviewed the literature of the last 10 y with the aim to give an up-to-date overview on processing/storage parameters, antistaling ingredients, sourdough technology, and measurement methods of the staling phenomenon. Many researchers have been focusing their interest on the selection of ingredients able to retard staling, mainly hydrocolloids, waxy wheat flours (WWF), and enzymes, but different efforts have been made to understand the molecular basis of bread staling with the help of various measurement methods. Results obtained confirm the central role of amylopectin retrogradation and water redistribution within the different polymers in determining bread staling, but highlighted also the importance of other flour constituents, such as proteins and nonstarch polysaccharides. Data obtained with thermal, spectroscopy, nuclear magnetic resonance, X-ray crystallography, and colorimetry analysis have pointed out the need to encourage the use of one or more of these techniques in order to better understand the mechanisms of staling. Results so far obtained have provided new insight on bread staling, but the phenomenon has not been fully elucidated so far.

Response surface optimization for xylanase with high volumetric productivity by indigenous alkali tolerant Aspergillus candidus under submerged cultivation

In this study, a novel isolate Aspergillus candidus was employed for xylanase production using low cost agro residues. A Box-Behnken design matrix was used to optimize the influential parameters like carbon source, nitrogen source and incubation temperature for maximum xylanase production. Under optimized condition, enzyme titer level enhanced to 69 IU/ml at 48 h with volumetric productivity 1437 IU/l h. Growth and enzyme production were observed even at pH 11.0, indicating its ability to sustain at high alkaline environment. Little amount of cellulase was produced concomitantly with xylanase during the course of the process. Volumetric productivity of xylanase was found as a function of temperature. This fungal strain was emerged as a one among few strains having high xylanase productivity.