Production, Purification of Exo-Polygalacturonase from Soil Isolate Paecilomyces variotii NFCCI 1769 and Its Application

Fungal pectinases: an insight into production, innovations and applications

The fungal system holds morphological plasticity and metabolic versatility which makes it unique. Fungal habitat ranges from the Arctic region to the fertile mainland, including tropical rainforests, and temperate deserts. They possess a wide range of lifestyles behaving as saprophytic, parasitic, opportunistic, and obligate symbionts. These eukaryotic microbes can survive any living condition and adapt to behave as extremophiles, mesophiles, thermophiles, or even psychrophile organisms. This behaviour has been exploited to yield microbial enzymes which can survive in extreme environments. The cost-effective production, stable catalytic behaviour and ease of genetic manipulation make them prominent sources of several industrially important enzymes. Pectinases are a class of pectin-degrading enzymes that show different mechanisms and substrate specificities to release end products. The pectinase family of enzymes is produced by microbial sources such as bacteria, fungi, actinomycetes, plants, and animals. Fungal pectinases having high specificity for natural sources and higher stabilities and catalytic activities make them promising green catalysts for industrial applications. Pectinases from different microbial sources have been investigated for their industrial applications. However, their relevance in the food and textile industries is remarkable and has been extensively studied. The focus of this review is to provide comprehensive information on the current findings on fungal pectinases targeting diverse sources of fungal strains, their production by fermentation techniques, and a summary of purification strategies. Studies on pectinases regarding innovations comprising bioreactor-based production, immobilization of pectinases, in silico and expression studies, directed evolution, and omics-driven approaches specifically by fungal microbiota have been summarized.

Metabolic engineering of Bacillus subtilis with an endopolygalacturonase gene isolated from Pectobacterium. carotovorum; a plant pathogenic bacterial strain

Pectinolytic enzymes or pectinases are synthesized naturally by numerous microbes and plants. These enzymes degrade various kinds of pectin which exist as the major component of the cell wall in plants. A pectinase gene encoding endo-polygalacturonase (endo-PGase) enzyme was isolated from Pectobacterium carotovorum a plant pathogenic strain of bacteria and successfully cloned into a secretion vector pHT43 having σ^A-dependent promoter for heterologous expression in Bacillus subtilis (WB800N).The desired PCR product was 1209bp which encoded an open reading frame of 402 amino acids. Recombinant proteins showed an estimated molecular weight of 48 kDa confirmed by sodium dodecyl sulphate–polyacrylamide-gel electrophoresis. Transformed B. subtilis competent cells harbouring the engineered pHT43 vector with the foreign endo-PGase gene were cultured in 2X-yeast extract tryptone medium and subsequently screened for enzyme activity at various temperatures and pH ranges. Optimal activity of recombinant endo-PGase was found at 40°C and pH 5.0. To assay the catalytic effect of metal ions, the recombinant enzyme was incubated with 1 mM concentration of various metal ions. Potassium chloride increased the enzyme activity while EDTA, Zn⁺⁺ and Ca⁺⁺, strongly inhibited the activity. The chromatographic analysis of enzymatic hydrolysates of polygalacturonic acid (PGA) and pectin substrates using HPLC and TLC revealed tri and tetra-galacturonates as the end products of recombinant endo-PGase hydrolysis. Conclusively, endo-PGase gene from the plant pathogenic strain was successfully expressed in Bacillus subtilis for the first time using pHT43 expression vector and could be assessed for enzyme production using a very simple medium with IPTG induction. These findings proposed that the Bacillus expression system might be safer to escape endotoxins for commercial enzyme production as compared to yeast and fungi. Additionally, the hydrolysis products generated by the recombinant endo-PGase activity offer their useful applications in food and beverage industry for quality products.

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.

Status of the application of exogenous enzyme technology for the development of natural plant resources

Exogenous enzymes are extraneous enzymes that are not intrinsic to the subject. The exogenous enzyme industry has been rapidly developing recently. Successful application of recombinant DNA amplification, high-efficiency expression, and immobilization technology to genetically engineered bacteria provides a rich source of enzymes. Amylase, cellulase, protease, pectinase, glycosidase, tannase, and polyphenol oxidase are among the most widely used such enzymes. Currently, the application of exogenous enzyme technology in the development of natural plant resources mainly focuses on improving the taste and flavor of the product, enriching the active ingredient contents, deriving and transforming the structure of a chosen compound, and enhancing the biological activity and utilization of the functional ingredient. In this review, we discuss the application status of exogenous enzyme technology for the development of natural plant resources using typical natural active ingredients from plant, such as resveratrol, steviosides, catechins, mogrosides, and ginsenosides, as examples, to provide basis for further exploitation and utilization of exogenous enzyme technology.

Genomic and Genetic Insights Into a Cosmopolitan Fungus, Paecilomyces variotii (Eurotiales)

Species in the genus Paecilomyces, a member of the fungal order Eurotiales, are ubiquitous in nature and impact a variety of human endeavors. Here, the biology of one common species, Paecilomyces variotii, was explored using genomics and functional genetics. Sequencing the genome of two isolates revealed key genome and gene features in this species. A striking feature of the genome was the two-part nature, featuring large stretches of DNA with normal GC content separated by AT-rich regions, a hallmark of many plant-pathogenic fungal genomes. These AT-rich regions appeared to have been mutated by repeat-induced point (RIP) mutations. We developed methods for genetic transformation of P. variotii, including forward and reverse genetics as well as crossing techniques. Using transformation and crossing, RIP activity was identified, demonstrating for the first time that RIP is an active process within the order Eurotiales. A consequence of RIP is likely reflected by a reduction in numbers of genes within gene families, such as in cell wall degradation, and reflected by growth limitations on P. variotii on diverse carbon sources. Furthermore, using these transformation tools we characterized a conserved protein containing a domain of unknown function (DUF1212) and discovered it is involved in pigmentation.

Neosartorya glabra polygalacturonase produced from fruit peels as inducers has the potential for application in passion fruit and apple juices

Summary Polygalacturonases are enzymes with the biotechnological potential for use in fruit juice clarification and for the enhancement of filtration efficiency. The aim of this work was to assess the production of polygalacturonase by the fungus Neosartorya glabra by means of solid-state and submerged fermentation using fruit peel residues as the carbon source, and also apply the enzyme in the clarification and decrease in viscosity of passion fruit and apple juices. The highest polygalacturonase (4.52 U/g/h) production was obtained by means of submerged fermentation in Vogel´s medium (1964) containing orange peel – Bahia variety (Citrus sinensis), at a concentration of 1.5% (w/v, dried mass) at 30-35°C for 72 h. The polygalacturonase of the crude extract presented optimal activity at 60°C and pH 5.5. The enzyme retained around 90% of the initial activity after 180 minutes at 40°C, and 50% of the initial activity after 150 minutes at 50°C. The enzyme was shown to be stable at acid pH values (3.0-6.5) after 120 minutes at 25oC. All these favourable enzymatic properties make the polygalacturonase attractive for potential uses in the industry of pectin-rich fruit juices, since the application of the crude extract to passion fruit (Passiflora edulis) juice caused an 80% reduction in viscosity and 75% decrease in light absorbance. In the processing of apple pulp juice (Malus domestica), there was a 50% reduction in viscosity and 78% decrease in light absorbance.

Purification and characterization of polygalacturonase from Aspergillus fumigatus MTCC 2584 and elucidating its application in retting of Crotalaria juncea fiber

Polygalacturonases represents an important member of pectinases group of enzymes with diverse industrial applications and is widely distributed among fungi, bacteria, yeasts, plants and some plant parasitic nematodes. An endo-polygalacturonase from a new fungal source Aspergillus fumigatus MTCC 2584 was produced under solid-state fermentation conditions and was purified simply by acetone precipitation and gel-filtration chromatography technique. The approximate molecular weight of the purified PG was found to be 43.0 kDa as revealed by SDS-PAGE. The pH optimum of the purified enzyme was found to be 10.0 and was stable in the pH range of 7-10. The optimum temperature of purified PG was found to be 30 °C. The Km and Kcat of the purified enzyme were 2.4 mg/ml and 44 s-1, respectively, and the metal ions Cu2+ and K+ were found to enhance the enzyme activity while Ag+, Ca2+ and Hg2+ were inhibitory in nature. Based on its alkaline nature, the potential of purified PG in retting of natural fiber Crotalaria juncea was elucidated in the absence of EDTA. This is probably the first report of alkaline PG from Aspergillus fumigatus.

Enhanced production of pectinase by Aspergillus terreus NCFT 4269.10 using banana peels as substrate

Aspergillus terreus NCFT4269.10 was implemented in solid-state (SSF) and liquid static surface fermentation (LSSF) for biosynthesis of pectinase. Amongst various substrates, like, mustard oil cake, neem oil cake, groundnut oil cake, black gram peels, green gram peels, chickling vetch peels/grass pea peels wheat bran, pearl millet residues, finger millet waste, broken rice, banana peels (BP), apple pomace (AP) and orange peels, banana peel (Musa paradisiaca L.; Family: Musaceae) was most suitable for pectinase biosynthesis (LSSF: 400 ± 21.45 Uml⁻¹; SSF: 6500 ± 1116.21 Ug⁻¹). Optimization of process parameters using one-variable-at-a-time method revealed that an initial medium pH of 5.0 at 30 °C and 96 h of incubation along with mannitol, urea, ammonium persulfate and isoleucine have positive influence on pectinase production. Further, K⁺ (1 mM), Riboflavin (10 mg 100 ml⁻¹) and gibberellic acid (0.025 %, w/v) supported in enhanced pectinase production. Banana peels and AP at a ratio of 9:1, moisture content of 90 % with 2 % inoculum size were suitable combinations for production of pectinase. Similarly, 96 h of soaking time with 0.1 M phosphate buffer (pH 6.5) is essential for pectinase recovery. Purification to electrophoretic homogeneity revealed 1.42 fold purification with 8.08 % yield and a molecular weight of 24.6 kDa. Scaling up of various fermentation parameters and supplementing BP as the substrate for pectinase production with better recovery could make it promising for different industrial exploitation.

Enzymes and bioproducts produced by the ascomycete fungus Paecilomyces variotii

Due its innate ability to produce extracellular enzymes which can provide eco-friendly solutions for a variety of biotechnological applications, Paecilomyces variotii is a potential source of industrial bioproducts. In this review, we report biotechnological records on the biochemistry of different enzymes produced by the fermentation of the P. variotii fungus, including tannases, phytases, cellulases, xylanases, chitinases, amylases and pectinases. Additionally, the main physicochemical properties which can affect the enzymatic reactions of the enzymes involved in the conversion of a huge number of substrates to high-value bioproducts are described. Despite all the background information compiled in this review, more research is required to consolidate the catalytic efficiency of P. variotii, which must be optimized so that it is more accurate and reproducible on a large scale.

Preliminary Extraction and Identification of the 44.5 kDa Outer Membrane Proteins Isolated from Bovine Fusobacterium necrophorum (AB)

Fusobacterium necrophorum (AB) in the pharynx, respiratory tract, female reproductive tract or urinary system is the causative agent of footrot and hepatic abscesses in animals and acute Lemierre's syndrome in humans. Current methods do not effectively protect animals and humans against F. necrophorum (AB). The outer membrane proteins (OMP) of F. necrophorum (AB) can be used as new material to protect against the diseases induced by F. necrophorum (AB). The aim of this study was to extract OMP and examine the immunogenic response of OMP. The preliminary extraction of OMP of F. necrophorum (AB) was identified by SDS-PAGE and stained by Coomassie Brilliant Blue R-250 (CB B R-250) and silver staining methods. The results showed that only a major band of 44.5 kDa was observed when staining the gel using CB B R-250. This band represented the target protein. In contrast, many small bands were observed by the silver staining method. The OMP also exhibited immune biological activities according to western blot analysis. The brightest band among the multi-banding observed was the OMP. Thus, the OMP was obtained and had immunogenic activity. The results provide a new direction to protect animals and humans against F. necrophorum (AB) in the clinical setting.