Kinetic study of a β-mannanase from the Bacillus licheniformis HDYM-04 and its decolorization ability of twenty-two structurally different dyes

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.

Application of the immobilized enzyme on magnetic graphene oxide nano-carrier as a versatile bi-functional tool for efficient removal of dye from water

Herein, we report bi-functional applications of a novel immobilized enzyme on the modified magnetic graphene oxide (GO) for effective removal of dyes from water. The amine functionalized GO nano-carrier was covalently attached to a model enzyme (PersiManXyn1). The enzyme assays showed that the specific activities of the free and immobilized enzyme were 856.05 and 1141.1 µmolmin^-1mg^-1, respectively. While the free enzyme showed only 5% of its maximum activity, the immobilized PersiManXyn1 preserved more than 35% of its activity, at 90 °C. After four weeks storage, the free enzyme has been deactivated, but the immobilized enzyme retained 54% of its initial activity. The immobilized PersiManXyn1 was proficiently applied for dye removal from water using two strategies. While only pristine nano-carrier and free enzyme showed no considerable catalytic ability, the immobilized PersiManXyn1 could catalytically reduce the concentrated dye solutions within 150 s with superior reusability (94% dye removal after 15^th cycle). Proficient treatment of a real textile effluent by the immobilized PersiManXyn1 approved its practical applications in the water remediation.

Characterization of a thermotolerant and acidophilic mannanase producing Microbacterium sp. CIAB417 for mannooligosachharide production from agro-residues and dye decolorization

Mannanases are ubiquitous enzymes and are being explored for diverse industrial applications. In this study, a novel bacterial strain Microbacterium sp. CIAB417 was identified and characterized for extracellular production of mannanase. Microbacterium sp. CIAB417 was found to produce maximum mannanase after 36 h of incubation at 37 °C. Mannanase produced by the isolate was observed for maximum activity at optimum pH of 6 and optimum temperature of 50 °C. Crude mannanase was found to be capable of producing mannooligosachharides (MOS) by hydrolyzing hemicellulose from locust bean gum and Aloe vera. The produced MOS was characterized and found to be mixture of mannobiose to mannohexose units. Mannanase was also explored for decolorization of dyes. Bromophenol blue and coomassie blue R-250 were observed to be decolorized to the extent of 45.40 and 42.75%, respectively. Hence, the identified bacterial strain producing mannanase could be of great significance for applications in food and textile industry.

Purification and characterization of novel thermostable and Ca-independent α-amylase produced by Bacillus amyloliquefaciens BH072

In the present study, a novel α-amylase produced by Bacillus amyloliquefaciens BH072 was purified and characterized. The molecular weight of purified α-amylase was approximately 68 kDa, determined by Sodium Dodecyl Sulfate Polyacrylamide Gel Electrophoresis (SDS-PAGE) and ten amino acid of N-terminal was NSGLNGYLTH. The kinetic parameters K_m and V_max were 4.27 ± 0.21 mg/mL and 987.34 ± 23.34 U/mg, respectively. Purified α-amylase showed maximal activity at pH 7 and 60 °C. Enzyme remained stable in pH range 6.0-7.0 and 50-80 °C. The activity of the α-amylase was Ca²⁺ independent and stability in the presence of surfactant, oxidizing and bleaching agents. The β-mercaptoethanol and EDTA greatly enhanced and reduced α-amylase activity, respectively. This enzyme has high hydrolysis rate toward corn, wheat and potato starch and hydrolyzes soluble starch to glucose, maltose, maltotriose and maltotetraose, indicating that the α-amylase represents a promising candidate for applications in the food industry.

Bacillus Cellulase Molecular Cloning, Expression, and Surface Display on the Outer Membrane of Escherichia coli

One of the main challenges of using recombinant enzymes is that they are derived from genetically-modified microorganisms commonly located in the intracellular region. The use of these recombinant enzymes for commercial purposes requires the additional processes of cell disruption and purification, which may result in enzyme loss, denaturation, and increased total production cost. In this study, the cellulase gene of Bacillus licheniformis ATCC 14580 was cloned, over-expressed, and surface displayed in recombinant Escherichia coli using an ice-nucleation protein (INP). INP, an outer membrane-bound protein from Pseudomonas syringae, was utilized as an anchor linker, which was cloned with a foreign cellulase gene into the pET21a vector to develop a surface display system on the outer membrane of E. coli. The resulting strain successfully revealed cellulase on the host cell surface. The over-expressed INP-cellulase fusion protein was confirmed via staining assay for determining the extracellular cellulase and Western blotting method for the molecular weight (MW) of cellulase, which was estimated to be around 61.7 kDa. Cell fractionation and localization tests demonstrated that the INP-cellulase fusion protein was mostly present in the supernatant (47.5%) and outer membrane (19.4%), while the wild-type strain intracellularly retained enzymes within cytosol (>61%), indicating that the INP gene directed the cellulase expression on the bacteria cell surface. Further studies of the optimal enzyme activity were observed at 60 °C and pH 7.0, and at least 75% of maximal enzyme activity was preserved at 70 °C.