Production and Optimization of Pectinase from Pectinolytic Fungi Cultivated on Mango peels and Pectin Subjected to Submerged Fermentation

Pectinases are the group of enzymes that degrade pectin. This study was conducted with the aim of isolation of efficient pectinase producing pectinolytic fungi from the decomposing mango peels using extracted mango peels pectin as a growth substrate under submerged fermentation, determining optimum pectinase production conditions with regards to some physicochemical parameters. The organisms were screened for the production of pectinase using Pectin agar media, and the two active pectinolytic fungi (P1 and P2) were isolated. pectinase production media was later used for the Lab scale production of pectinase by inoculating p1 and p2 and incubating for 7 days. The enzyme was extracted after seven days of fermentation and every day tested for their pectinolytic activity. P2 showed relatively higher pectinolytic activity and was therefore used for further studies. P2 was inoculated into a broth containing mango pectin under submerged fermentation. Results indicate that a pectin yield of mango peel 17.75%. Different parameters optimization processes were investigated on submerged fermentation namely pH, incubation period, temperature and substrate concentration optima were found 6, 4 days, 35oC and 1.5% respectively. The result suggests that mango peels have high pectin content and can be used for the value-added synthesis of pectinase.

Pectinolytic activity of aspergillus niger and Aspergillus flavus grown on grapefruit (citrus Parasidis) peel in solid state fermentation

The present study was aimed at studying pectinolytic activity of resident fungi isolated from decomposing grapefruit (Citrus parasidis) peels in solid state fermentation. Grape fruit peel was subjected to natural fermentation and the fermenting fungi were isolated, characterized and identified using standard microbiological methods. The isolated fungi were in turn used for fermentation to determine their pectinolytic activity through solid state fermentation technique. Culture parameters such as incubation period, temperature, moisture content and addition of salts supplements were optimized during the research for five days. The identified fungi were Aspergillus Niger and Aspergillus flavus. The peak of pectinolytic activity was at day three of fermentation when the highest pectinase activity of 13.32 μmol/mg/min was recorded for A. Niger and 11.32 μmol/mg/min for A. flavus. Optimum temperature and pH for pectinase activity by A. Niger and A. flavus was at 40 0C and pH 7.5 and 7.7 respectively. The use of salt supplemented substrate did not alter enzyme activity. In conclusion, the isolated fungi could be promising organisms for pectinolytic enzyme production on grape peel as substrate. Keywords: Grapefruit, Pectinolytic Activity, Fungi, Fermentation, Aspergillus

Lactic Acid Bacteria in Wine: Technological Advances and Evaluation of Their Functional Role

Currently, the main role of Lactic Acid Bacteria (LAB) in wine is to conduct the malolactic fermentation (MLF). This process can increase wine aroma and mouthfeel, improve microbial stability and reduce the acidity of wine. A growing number of studies support the appreciation that LAB can also significantly, positively and negatively, contribute to the sensorial profile of wine through many different enzymatic pathways. This is achieved either through the synthesis of compounds such as diacetyl and esters or by liberating bound aroma compounds such as glycoside-bound primary aromas and volatile thiols which are odorless in their bound form. LAB can also liberate hydroxycinnamic acids from their tartaric esters and have the potential to break down anthocyanin glucosides, thus impacting wine color. LAB can also produce enzymes with the potential to help in the winemaking process and contribute to stabilizing the final product. For example, LAB exhibit peptidolytic and proteolytic activity that could break down the proteins causing wine haze, potentially reducing the need for bentonite addition. Other potential contributions include pectinolytic activity, which could aid juice clarification and the ability to break down acetaldehyde, even when bound to SO2, reducing the need for SO2 additions during winemaking. Considering all these findings, this review summarizes the novel enzymatic activities of LAB that positively or negatively affect the quality of wine. Inoculation strategies, LAB improvement strategies, their potential to be used as targeted additions, and technological advances involving their use in wine are highlighted along with suggestions for future research.

Production, Characterization, and Industrial Application of Pectinase Enzyme Isolated from Fungal Strains

Pectinases are the group of enzymes that catalyze the degradation of pectic substances. It has wide applications in food industries for the production and clarification of wines and juices. The aim of this study was to isolate, screen and characterize pectinase from fungi isolated from various soil samples and evaluate its application in juice clarification. Fungal strains were isolated and screened primarily using 1% citruspectin incorporated potato dextrose agar (PDA) and secondarily using pectinase screening agar medium (PSAM) for pectinolytic organisms. The enzyme was produced by submerged state fermentation and assayed using the dinitro salicylic acid (DNS) method. From 20 different soil samples, 55 fungal isolates were screened primarily and, among them, only 14 isolates were subjected for secondary screening. Out of 14, only four strains showed the highest pectinolytic activity. Among four strains, Aspergillus spp. Gm showed the highest enzyme production at a 48-h incubation period, 1% substrate concentration, and 30 °C temperature. The thermal stability assessment resulted that the activity of pectinase enzyme declines by 50% within 10 min of heating at 60 °C. The optimum temperature, pH, and substrate concentration for the activity of enzyme was 30 °C (75.4 U/mL), 5.8 (72.3 U/mL), and 0.5% (112.0 U/mL), respectively. Furthermore, the yield of the orange juice, the total soluble solid (TSS), and clarity (% transmittance) was increased as the concentration of the pectinase increased, indicating its potential use in juice processing. Overall, the strain Aspergillus spp. Gm was identified as a potent strain for pectinase production in commercial scale.

The metabolic shift in highly and weakly virulent Dickeya solani strains is more affected by temperature than by mutations in genes encoding global virulence regulators

ABSTRACT Global warming may shortly increase the risk of disease development on plants. Significant differences in the metabolic activity screened with Phenotype Microarray at 22°C and 28°C were observed between D. solani strains with high and low virulence level. Highly virulent D. solani was characterized by a higher number of metabolized compounds and a faster metabolism and was more tolerant to non-favorable pH and osmolarity. Metabolic phenotyping showed for the first time that the mutation in pecT gene, which encodes a global repressor of virulence, affects several pathways of the basic cell metabolism. PecT mutants had a higher maceration capacity of potato tissue and showed a higher pectinolytic activity than the wild-type strains. On the contrary, mutation in expI gene, which encoded the signaling molecules synthase crucial for quorum sensing, had an insignificant effect on the cell metabolism, although it slightly reduced the potato tissue maceration. The ability to utilize most of the tested compounds was higher at 28°C, while the survival at non-favorable pH and osmolarity was higher at 22°C. These results proved that the temperature of incubation had the most significant impact on the D. solani metabolic profiles.

Comparative evaluation of Aspergillus niger strains for endogenous pectin depolymerization capacity and suitability for D-galacturonic acid production

Pectinaceous agricultural residues rich in d-galacturonic acid (d-GalA), such as sugar beet pulp, are considered as promising feedstocks for waste-to-value conversions. Aspergillus niger is known for its strong pectinolytic activity. However, while specialized strains for production of citric acid or proteins are openly available, this is not the case for the production of pectinases. We therefore systematically compared the pectinolytic capabilities of six A. niger strains (ATCC 1015, ATCC 11414, NRRL 3122, CBS 513.88, NRRL 3, N402) using controlled batch cultivations in stirred-tank bioreactors. A. niger ATCC 11414 showed the highest polygalacturonase activity, specific protein secretion and a suitable morphology. Furthermore, d-GalA release from sugar beet pulp was 75% higher compared to the standard lab strain A. niger N402. Our study therefore presents a robust initial strain selection to guide future process improvement of d-GalA production from agricultural residues and identifies the most suitable base strain for further genetic optimizations.

Oligogalacturonide production upon Arabidopsis thaliana–Botrytis cinerea interaction

Despite an ever-increasing interest for the use of pectin-derived oligogalacturonides (OGs) as biological control agents in agriculture, very little information exists—mainly for technical reasons—on the nature and activity of the OGs that accumulate during pathogen infection. Here we developed a sensitive OG profiling method, which revealed unsuspected features of the OGs generated during infection of Arabidopsis thaliana with the fungus Botrytis cinerea. Indeed, in contrast to previous reports, most OGs were acetyl- and methylesterified, and 80% of them were produced by fungal pectin lyases, not by polygalacturonases. Polygalacturonase products did not accumulate as larger size OGs but were converted into oxidized GalA dimers. Finally, the comparison of the OGs and transcriptomes of leaves infected with B. cinerea mutants with reduced pectinolytic activity but with decreased or increased virulence, respectively, identified candidate OG elicitors. In conclusion, OG analysis provides insights into the enzymatic arms race between plant and pathogen and facilitates the identification of defense elicitors.

Commercial Saccharomyces cerevisiae Yeast Strains Significantly Impact Shiraz Tannin and Polysaccharide Composition with Implications for Wine Colour and Astringency

To gain knowledge on the role of Saccharomyces cerevisiae yeast strains (and their hybrids) on wine sensory properties, 10 commercially available yeast strains were selected on the basis of their widespread usage and/or novel properties and used to produce Shiraz wines. Significant differences were evident post-alcoholic fermentation and after 24 months of ageing with regards to the number of wine compositional variables, in particular the concentration of tannin and polysaccharide. Strain L2323 is known for its pectinolytic activity and yielded the highest concentration of both yeast- and grape-derived polysaccharides. Wines made with the mannoprotein-producing strain Uvaferm HPS (high levels of polysaccharides) did not have elevated concentrations of yeast-derived polysaccharides, despite this observation being made for corresponding model fermentations, suggesting that mannoprotein production or retention might be limited by the wine matrix. Wine tannin concentration showed a high level of variability between strains, with L2323 having the highest, and AWRI1503 the lowest concentration. Sensory analysis of the wines after 24 months ageing revealed significant differences between the yeast strains, but only the attributes opacity (visual colour) and astringency could be predicted by partial least squares regression using the wine compositional data. Notably, the astringency attribute was associated with higher concentrations of both tannin and polysaccharide, contrary to reports in the literature which suggested that polysaccharide exerts a moderating effect on astringency. The results confirm previous reports demonstrating that the choice of yeast strain represents an opportunity to shape wine style outcomes.

Isolation and Screening of Pectinolytic Bacterial Strains using Rotten Apples from Lahore, Pakistan

Pectinases are pectin degrading enzymes predominantly used as biocatalysts in various industries such as wine extraction, fruit juice extraction, and making of paper pulp. Large scale production of pectinases using biological systems (bacteria, fungi, plants) is a common method used in the industry. In the current study, different bacterial isolates obtained from rotten apples were used for pectinase production and their pectinolytic activity was investigated. Five bacterial strains were isolated on the growth medium containing 0.3% KH2PO4, 0.6% Na2HPO4, 0.2% NH4Cl, 0.5% NaCl, 1% Pectin, 1.5% Agar, 1mM CaCl2, and 10mM MgSO4. The isolates of five samples A, B, C, D and E were then biochemically characterized as Serratia marcescens, Klebseilla pneumoniea, Pseudomonas aeruginosa and Escherichia coli, respectively. They were also identified at the molecular level through 16S rRNA gene sequencing.

Extracellular Production of Pectinase from Bacteria Isolated from Rotten Apples from Lahore, Pakistan

Pectins are intricate blends of polysaccharides which make up around 33% of plantcell wall. Despite of their presence in the greater part of plant body and in other sources, commercial production of pectin is extremely difficult. This is a systematic study that aimed to produce pectinase from bacterial species isolated from rotten apple samples. Zymography and enzyme assay through DNS method were performed to check the pectinolytic activity of bacteria isolated from rotten apple samples. Of all five bacterial species (Serratia marcescens, Klebseilla pneumoniea, Pseudomonas aeruginosa and Escherichia coli) maximum enzyme concentration was showed in Pseudomonas aeruginosa and it was 6.2 U/mL. The major achievement of this study was to screen out the most efficient pectinases producing isolate of Serratia marcescens from rotten apples that has never been reported to produce pectinase, previously.