Thermostable and organic solvent-tolerant acid pectinase from Aspergillus terreus FP6: purification, characterization and evaluation of its phytopigment extraction potential

The present study discusses the purification, characterization and application of pectinase from Aspergillus terreus FP6 in fruit pigment extraction. By the four-step purification involving precipitation, dialysis, ion-exchange chromatography, gel filtration chromatography, a 20.85-fold purification of the enzyme to homogeneity was achieved. The apparent molecular mass of the pectinase was 47 kDa, as found by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. The optimum activity of the enzyme was recorded at pH 6.0 and 50 °C. The enzyme retained 80.3% and 79.1% residual activity, respectively at pH 6.0 and 50 °C for 90 min. The pectinase was best functional in the presence of toluene and retained its activity for 30 min. Cu²⁺ and Co²⁺ acted as enzyme activators, while Ca²⁺, β-mercaptoethanol, dimethyl sulfoxide and ethylenediaminetetraacetic acid proved to be the inhibitors. The K _m and V _max values of the pectinase with pectin as substrate were 0.002 mM and 27.39 U/mL, respectively thus indicating the high enzyme affinity towards the substrate. After 30-min treatment of the grape skin with the partially purified enzyme, microscopic observation revealed that a short time of the enzymatic treatment resulted in substantial loss of pigment and shrinkage of the grape skin cells thereby highlighting the high efficiency of the pectinase. The current study implies that the A. terreus FP6 pectinase may be applied as a bio-agent in the food and beverage industries and has the potential to replace harmful solvents by promoting a greener approach to extract plant pigments.

From secretion in Pichia pastoris to application in apple juice processing: Exo-polygalacturonase from Sporothrix schenckii 1099-18

BACKGROUND

Polygalacturonases are a group of enzymes under pectinolytic enzymes related to enzymes that hydrolyse pectic substances. Polygalacturonases have been used in various industrial applications such as fruit juice clarification, retting of plant fibers, wastewater treatment drinks fermentation, and oil extraction.

OBJECTIVES

The study was evaluated at the heterologous expression, purification, biochemical characterization, computational modeling, and performance in apple juice clarification of a new exo-polygalacturonase from Sporothrix schenckii 1099-18 (SsExo-PG) in Pichia pastoris.

METHODS

Recombinant DNA technology was used in this study. Two different pPIC9K plasmids were constructed with native signal sequence-ssexo-pg and alpha signal sequence-ssexo-pg separately. Protein expression and purification performed after plasmids transformed into the Pichia pastoris. Biochemical and structural analyses were performed by using pure SsExo-PG.

RESULTS

The purification of SsExo-PG was achieved using a Ni-NTA chromatography system. The enzyme was found to have a molecular mass of approximately 52 kDa. SsExo-PG presented as stable at a wide range of temperature and pH values, and to be more storage stable than other commercial pectinolytic enzyme mixtures. Structural analysis revealed that the catalytic residues of SsExo-PG are somewhat similar to other Exo-PGs. The KM and kcat values for the degradation of polygalacturonic acid (PGA) by the purified enzyme were found to be 0.5868 µM and 179 s-1, respectively. Cu2+ was found to enhance SsExo-PG activity while Ag2+ and Fe2+ almost completely inhibited enzyme activity. The enzyme reduced turbidity up to 80% thus enhanced the clarification of apple juice. SsExo-PG showed promising performance when compared with other commercial pectinolytic enzyme mixtures.

CONCLUSION

The clarification potential of SsExo-PG was revealed by comparing it with commercial pectinolytic enzymes. The following parameters of the process of apple juice clarification processes showed that SsExo-PG is highly stable and has a novel performance.

Acetylcholinesterases from Leaf-Cutting ant Atta sexdens: Purification, Characterization, and Capillary Reactors for On-Flow Assays

Acetylcholinesterase (AChE) is responsible for catalyzing the hydrolysis of the neurotransmitter acetylcholine (ACh) leading to acetate and choline (Ch) release. The inhibition of AChE produces a generalized synaptic collapse that can lead to insect death. Herein we report for the first time the isolation of two AChEs from Atta sexdens which were purified by sulphate ammonium precipitation followed by ion exchange chromatography. AsAChE-A and AsAChE-B enzymes have optimum pH of 9.5 and 9.0 and higher activities in 30/50°C and 20°C, respectively, using acetylthiocholine (ATCh) as substrate. Immobilized capillary enzyme reactors (ICERs) were obtained for both enzymes (AsAChE-A-ICER and AsAChE-B-ICER) and their activities were measured by LC-MS/MS through hydrolysis product quantification of the natural substrate ACh. The comparison of activities by LC-MS/MS of both AChEs using ACh as substrate showed that AsAChE-B (free or immobilized) had the highest affinity. The inverse result was observed when the colorimetric assay (Elman method) was used for ATCh as substrate. Moreover, by mass spectrometry and phylogenetic studies, AsAChE-A and AsAChE-B were classified as belonging to AChE-2 and AChE-1 classes, respectively.