Molecular dynamic simulation studies of bacterial thermostable mannanase unwinding the enzymatic catalysis

Improvement of the Catalytic Ability of a Thermostable and Acidophilic β-Mannanase Using a Consensus Sequence Design Strategy

In order to improve the catalytic efficiency of a thermostable and acidophilic β-mannanase (ManAK; derived from marine Aspergillus kawachii IFO 4308), three mutants were designed by amino acid sequence consensus analysis with a second β-mannanase (ManCbs), which also belongs to the glycoside hydrolase family 5 (GH5) and has excellent catalytic efficiency. Three mutants were constructed and their biochemical characteristics were measured after heterologous expression in Pichia pastoris. The results revealed that the kcat/Km values of the three recombinant mannanases ManAKC292V, ManAKL293V, and ManAKL294H were enhanced by 303.0, 280.4, and 210.1%, respectively. Furthermore, ManAKL293V showed greater thermostability than ManAK, retaining 36.5% of the initial enzyme activity after incubation at 80°C for 5min. This study therefore provides a rational design strategy based on consensus sequence analysis to develop industrially valuable β-mannanase for future applications in marine aquafeed.

Purification and Characterization of Mannanase from Aspergillus awamori for Fruit Juice Clarification

BACKGROUND

Fruit juice clarification is a challenging aspect of beverage industry which needs to be addressed for economical and hygienic production of fruit juices.

OBJECTIVE

Current study is focused on the complete purification, characterization and thermodynamic analysis of an efficient mannanase enzyme to analyze its applicability in biological clarification fruit juice.

METHODS

Mannanase production using Aspergillus awamori IIB037 in a 25 L stirred fermenter at pre optimized reaction conditions was carried out. Enzyme purification was carried out via series of steps. Characterization of enzyme along with kinetics and thermodynamic studies was conducted. Purified and characterized enzyme was assessed for its applicability in fruit juice clarification through clarification experiments on fresh apple juice.

RESULTS

Purification fold of 3.98 was obtained along with 86.80% purification yield of mannanase with specific activity of 158.16 U/mg. The molecular size of purified enzyme was determined as 66 kDa. The enzyme depicted 56% residual activity at 60°C after 8 hrs. Thermodynamic studies of an enzyme revealed enthalpy of activation (ΔH) and activation energy (Ea) as 30.53KJ/mol, 27.76KJ/mol, respectively. The enzyme activity increased in the presence of ß-mercaptoethanol surprisingly. On the other hand, methyl alcohol, ethanol, Hg2+ and Cu2+ inhibited enzyme activity. The enzyme showed Km and Vmax values of 11.07 mM and 19.08 μM min-1 for Locust Bean Gum (LBG) under optimal conditions. Juice treated with mannanase showed decrease in absorbance and increase in reducing sugar content.

CONCLUSION

The current study demonstrated that mannanase from Aspergillus awamori in its purified form has significant characteristics to be employed industrially for juice clarification.

Bacterial laccase: recent update on production, properties and industrial applications

Laccases (benzenediol: oxygen oxidoreductase, EC 1.10.3.2) are multi-copper enzymes which catalyze the oxidation of a wide range of phenolic and non-phenolic aromatic compounds in the presence or absence of a mediator. Till date, laccases have mostly been isolated from fungi and plants, whereas laccase from bacteria has not been well studied. Bacterial laccases have several unique properties that are not characteristics of fungal laccases such as stability at high temperature and high pH. Bacteria produce these enzymes either extracellularly or intracellularly and their activity is in a wide range of temperature and pH. It has application in pulp biobleaching, bioremediation, textile dye decolorization, pollutant degradation, biosensors, etc. Hence, comprehensive information including sources, production conditions, characterization, cloning and biotechnological applications is needed for the effective understanding and application of these enzymes at the industrial level. The present review provides exhaustive information of bacterial laccases reported till date.