Phylogenetic Analysis of Polygalacturonase-Producing Bacillus and Pseudomonas Isolated From Plant Waste Material

A specific innate immune response silences the virulence of Pseudomonas aeruginosa in a latent infection model in the Drosophila melanogaster host

Microbial pathogenicity often depends on the route of infection. For instance, P. aeruginosa or S. marcescens cause acute systemic infections when low numbers of bacteria are injected into D. melanogaster flies whereas flies succumb much slower to the continuous ingestion of these pathogens, even though both manage to escape from the gut compartment and reach the hemocoel. Here, we have developed a latent P. aeruginosa infection model by feeding flies on the bacteria for a short period. The bacteria stably colonize internal tissues yet hardly cause any damage since latently-infected flies live almost as long as noninfected control flies. The apparently dormant bacteria display particular characteristics in terms of bacterial colony morphology, composition of the outer cell wall, and motility. The virulence of these bacteria can however be reactivated upon wounding the host. We show that melanization but not the cellular or the systemic humoral response is the predominant host defense that establishes latency and may coerce the bacteria to a dormant state. In addition, the lasting activation of the melanization responses in latently-infected flies provides a degree of protection to the host against a secondary fungal infection. Latent infection by an ingested pathogen protects against a variety of homologous or heterologous systemic secondary infectious challenges, a situation previously described for the endosymbiotic Wolbachia bacteria, a guard against viral infections.

Utilization of wild Cressa cretica biomass for pectinase production from a halo-thermotolerant bacterium

Halophytes are the native inhabitants of saline environment. Their biomass can be considered as a potential substrate for the production of microbial enzymes. This study was intended at feasible utilization of a halophytic biomass, Cressia cretica, for pectinase production using a halo- and thermo-tolerant bacterium, Bacillus vallismortis MH 10. The data from fractionation of the C. cretica biomass revealed presence of 17% pectin in this wild biomass. Seven different factors (temperature, agitation, pH, inoculum size, peptone concentration, substrate concentration, and incubation time) affecting pectinase production using C. cretica were assessed through a statistical tool, Plackett-Burman design. Consequently, two significant factors (incubation time and peptone concentration) were optimized using the central composite design. The strain produced 20 IU mL-1 of pectinase after 24 h under optimized conditions. The enzyme production kinetics data also confirmed that 24 h is the most suitable cultivation period for pectinase production. Fourier transform infrared spectroscopy and scanning electron microscopy of C. cretica biomass ascertained utilization of pectin and structural changes after fermentation. The purification of pectinase by using DEAE column yielded specific activity and purification fold of 88.26 IU mg-1 and 3.2, respectively. The purified pectinase had a molecular weight of >65 kDa. This study offers prospects of large-scale production of pectinase by halotolerant strain in the presence of economical and locally grown substrate that makes the enzyme valuable for various industrial operations.

Pectinases as promising green biocatalysts having broad-spectrum applications: Recent trends, scope, and relevance

Pectinases are a collection of multiple enzymes that have a common substrate, that is, pectin. They can act on different parts of pectin due to the structural heterogeneity of pectin. Therefore, they have been placed in different groups, such as protopectinases, polygalacturonases, polymethylesterases, pectin lyases, and pectate lyases. They are naturally present both in multicellular organisms such as higher plants and in unicellular organisms such as microbes. In past decade, it has been witnessed that chemical and mechanical methods employed in industrial processes have led to environmental hazards and serious health disorders, thus increasing the search for eco-friendly approaches with minimal health risks. Hence, microbial enzymes have been extensively used as safer alternative for these environmentally unsafe methods. Among these microbial enzymes, pectinases hold great significance and is one of the principal enzymes that have been used commercially. It is predominantly used as a green biocatalyst for fruit, fiber, oil, textile, beverage, pulp, and paper industry. Thus, this review focuses on the structure of pectin, microbial sources of pectin, and principle industrial applications of pectinases.

What lies on macroalgal surface: diversity of polysaccharide degraders in culturable epiphytic bacteria

Macroalgal surface constitutes a peculiar ecological niche and an advantageous substratum for microorganisms able to degrade the wide diversity of algal glycans. The degrading enzymatic activities of macroalgal epiphytes are of paramount interest for the industrial by-product sector and biomass resource applications. We characterized the polysaccharide hydrolytic profile of bacterial isolates obtained from three macroalgal species: the red macroalgae Asparagopsis taxiformis and Sphaerococcus coronopifolius (Rhodophyceae) and the brown Halopteris scoparia (Phaeophyceae), sampled in South Portugal. Bacterial enrichment cultures supplemented with chlorinated aliphatic compounds, typically released by marine algae, were established using as inoculum the decaying biomass of the three macroalgae, obtaining a collection of 634 bacterial strains. Although collected from the same site and exposed to the same seawater seeding microbiota, macroalgal cultivable bacterial communities in terms of functional and phylogenetic diversity showed host specificity. Isolates were tested for the hydrolysis of starch, pectin, alginate and agar, exhibiting a different hydrolytic potential according to their host: A. taxiformis showed the highest percentage of active isolates (91%), followed by S. coronopifolius (54%) and H. scoparia (46%). Only 30% of the isolates were able to degrade starch, while the other polymers were degraded by 55-58% of the isolates. Interestingly, several isolates showed promiscuous capacities to hydrolyze more than one polysaccharide. The isolate functional fingerprint was statistically correlated to bacterial phylogeny, host species and enrichment medium. In conclusion, this work depicts macroalgae as holobionts with an associated microbiota of interest for blue biotechnologies, suggesting isolation strategies and bacterial targets for polysaccharidases' discovery.

Augmented Retting Effect on Kenaf Fibers Using Alkalophilic Pectinase-Producing Bacteria in Combination with Water Solvents

A degumming approach is used in this paper with alkalophilic pectinase-producing bacteria (APPB) and two sources of water solvents to address the existing conventional water retting complexities of kenaf. The incorporation of APPB was confirmed based on their retting feasibilities and multiple cell-wall-degrading enzymatic delicacy. The combinations of APPB with seawater offered retting achievements within six-day retting in non-sterile conditions. These retting niches showed maximum (14.67 U/mL) pectinase activity with fiber separation feasibilities of 4.75 Fried test score. The yielded fiber composition analysis showed a higher cellulose composition (84.65%) and the least amount of hemicellulose, pectin, and ligneous gummy substances. The transmission electron microscopy scan of the yielded fibers showed smooth fiber surfaces, 84.20 µm fiber diameter, and 7.65 g/tex fine fiber compared with uninoculated and combinations of freshwater treatments. The FTIR spectra revealed the cellulosic discrepancies of the retting treatments by monitoring O-H and C=O stretching at ~3300 cm−1 and ~1730 cm−1 wavenumbers. These findings are compelling to yield kenaf fibers of quality considering the existing retting difficulties.

Isolation and characterization of pectinase-producing bacteria (Serratia marcescens) from avocado peel waste for juice clarification

BACKGROUND

Bacterial pectinase is an enzyme that could be employed in numerous sectors to break down pectin polysaccharide compounds. The goal of this study is to find pectinase-producing bacteria in avocado peel waste and see if the pectinase enzyme produced can be used to make fruit juice clarification.

RESULTS

The researchers isolated four different bacterial strains from avocado peel waste samples. The potential two bacterial isolates that were identified as being Serratia marcescens and Lysinibacillus macrolides. Finally, the analysis of pectinase production and its application in fruit juice clarification were performed using one of the bacterial strains of Serratia marcescens. The clear apple, lemon, and mango juices were further processed to assess each juice's properties. The highest antioxidant activity was recorded in lemon juice samples. The lemon juice showed the highest total titratable acidity and total phenol content. Apple juices contained the highest total soluble solids, reducing sugar content, and viscosity and the mango juices have the maximum pH value recorded.

CONCLUSIONS

The pectinase isolated from the bacterium Serratia marcescens could clear fruit juices. This pectinase needs to be studied more to make sure it works better in the fruit industry and other businesses.

Characterisation of the symbionts in the Mediterranean fruit fly gut

Symbioses between bacteria and their insect hosts can range from loose associations through to obligate interdependence. While fundamental evolutionary insights have been gained from the in-depth study of obligate mutualisms, there is increasing interest in the evolutionary potential of flexible symbiotic associations between hosts and their gut microbiomes. Understanding relationships between microbes and hosts also offers the potential for exploitation for insect control. Here, we investigate the gut microbiome of a global agricultural pest, the Mediterranean fruit fly (Ceratitis capitata). We used 16S rRNA profiling to compare the gut microbiomes of laboratory and wild strains raised on different diets and from flies collected from various natural plant hosts. The results showed that medfly guts harbour a simple microbiome that is primarily determined by the larval diet. However, regardless of the laboratory diet or natural plant host on which flies were raised, Klebsiella spp. dominated medfly microbiomes and were resistant to removal by antibiotic treatment. We sequenced the genome of the dominant putative Klebsiella spp. (‘Medkleb’) isolated from the gut of the Toliman wild-type strain. Genome-wide ANI analysis placed Medkleb within the K. oxytoca / michiganensis group. Species level taxonomy for Medkleb was resolved using a mutli-locus phylogenetic approach - and molecular, sequence and phenotypic analyses all supported its identity as K. michiganensis. Medkleb has a genome size (5825435 bp) which is 1.6 standard deviations smaller than the mean genome size of free-living Klebsiella spp. Medkleb also lacks some genes involved in environmental sensing. Moreover, the Medkleb genome contains at least two recently acquired unique genomic islands as well as genes that encode pectinolytic enzymes capable of degrading plant cell walls. This may be advantageous given that the medfly diet includes unripe fruits containing high proportions of pectin. The results suggest that the medfly harbours a commensal gut bacterium that may have developed a mutualistic association with its host and provide nutritional benefits.

Pectinase from Microorganisms and Its Industrial Applications

The utilization of microbial pectinase in different industries has been increased in its world demand. The major sources of pectinase are microorganisms mainly bacteria, fungi and yeast. The utilization of low-cost agro-industrial wastes as substrates has been preferable in pectinase production. Pectinase production faced various parameters optimization constraints such as temperature, pH and production times which are the main factors in pectinase production. The pectinase enzyme is getting attention due to its several advantages; hence, it needs to be explored further to take its maximum advantage in different industries. This review discusses the pectin substance structure, substrate for pectinase production, factors influencing pectinase production, the industrial application of microbial pectinase and also discusses challenges and future opportunities of applying microbial pectinase in industry.

Screening of pectinase-producing bacteria from farmlands and optimization of enzyme production from selected strain by RSM

Pectinolytic enzymes that catalyze the breakdown of substrates containing pectin are widespread. Pectinases have potential applications in various industries, including food, animal feed, textile, paper, and fuel. In this study, one hundred bacterial isolates were collected from Marand city farmlands (Azarbaijan-E-Sharqi, Iran) and screened by MP medium on the base of pectinase activity considering the significance of pectinases. The results depicted that three isolates showed the most pectinase activity (more massive halo). The biochemical and molecular test results showed that the three screened bacteria were Enterobacter and named Enterobacter sp. MF41, Enterobacter sp. MF84, and Enterobacter sp. MF90. Enterobacter sp. MF84 had the largest halo, so this strain was selected for the study of its produced pectinase. The results exhibited that the produced enzyme has optimum temperature and pH for activity at 30 °C and in 9, respectively. Finally, the enzyme production by Enterobacter sp. MF84 is optimized using response surface methodology (RSM) considering four factors (NH₄Cl, K₂HPO₄, pectin, and incubation time) as variables. The results showed that the optimization procedure increased the enzyme production up to 12 times (from 1.16 to 14.16 U/mg). The Pareto analysis revealed that ammonium chloride has a significant role in decreasing the enzyme production, probably by inducing the nitrification pathway enzymes in the presence of organic nitrogen in Enterobacter sp. MF84.

Evaluation of process involved in the production of aromatic compounds in Gram-negative bacteria isolated from vanilla (Vanilla planifolia ex. Andrews) beans

AIM

The present investigation was aimed at isolating and identifying bacterial strains from cured vanilla beans. Additionally, the study focused on evaluating bacterial processes pertaining to the aromatic compounds production (ACP).

METHODS AND RESULTS

Three bacteria were isolated from Vanilla planifolia beans, previously subjected to the curing process. According to morphological, biochemical and 16S rRNA analysis, the strains were identified as Citrobacter sp., Enterobacter sp. and Pseudomonas sp. The polygalacturonase activity (PGA) was determined using the drop, cup-plate and DNS methods. Aromatic compounds production was analysed by cup-plate method using FA as substrate and quantified by high performance liquid chromatography (ppm), the functional groups of vanillic acid (VA) were identified by FT-IR and the aromatic compounds (AC) resistance was determined and reported as minimum inhibitory concentration. Citrobacter sp., Enterobacter sp. and Pseudomonas showed PGA (70·31 ± 364, 76·07 ± 12·47 and 51 ± 10·92 U ml^-1 respectively), were producers of VA (3·23 ± 0·49, 324 ± 41 and 265·99 ± 11·61 ppm respectively) and were resistant to AC.

CONCLUSIONS

The Gram-negative bacteria isolated from V. planifolia beans were responsible for ACP.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first evidence for the role of Gram-negative bacterial isolates from cured Mexican V. planifolia beans in the process related to ACP.

LC/MS detection of oligogalacturonic acids obtained from tragacanth degradation by pectinase producing bacteria

Tragacanth, a highly branched carbohydrate polymer isolated from Astragalus, is one of the most commonly used gums in food industry. The primary structure of tragacanth is composed of galacturonic acid monomers connected with α 1-4 links, and it is very similar to the pectin. Tragacanth degradation by microorganisms is significant in two aspects: first, food preservation and microbial growth control due to too much use of tragacanth in the food industry, second, therapeutic and pharmaceutical potential of obtained oligosaccharides. In the present study, we report three new strains of bacteria, Acinetobacter guillouiae strain TD1, Kosakonia sacchari strain TD2, and Bacillus vallismortis strain PD1 with the capability of growing in tragacanth as an only source of carbon and energy. The evolutionary history of the isolated strains was analyzed based on 16S rRNA gene sequences in MEGA7 using the neighbor-joining method. The production of di and tri galacturonic acid due to pectinase activities of the strains were detected by thin layer chromatography (TLC) and liquid chromatography/Mass spectroscopy (LC/MS) analysis. Here is the first report of the ability to grow in tragacanth and pectinase activity monitoring in bacteria. Our results revealed that all of the isolated strains are capable of degrading pectin and tragacanth to oligo-galacturonic acids. The obtained products, which have different structures depending on the tragacanth structures and types of pectinolytic enzymes, would show therapeutic and pharmaceutical potentials.

A Novel Non-Cumbersome Approach Towards Biosynthesis of Pectic-Oligosaccharides by Non-Aflatoxigenic Aspergillus sp. Section Flavi Strain EGY1 DSM 101520 through Citrus Pectin Fermentation

Pectic-Oligosaccharides (POS) have a growing potential in food and feed industries. To satisfy the demand of worldwide markets from POS and avoid the shortcomings of currently applied methodologies encountered in their preparation, the present study highlights a novel robust approach for POS biosynthesis. In the current approach, Aspergillus sp.section Flavi strain EGY1 DSM 101520 was grown on citrus pectin-based medium as a core POS production medium. POS' levels accumulated in the fungal fermentation broth were optimized through a three step sequential statistical mathematical methodology; Plackett-Burman design (PBD), Box-Behnken design (BBD) and canonical analysis. Three key determinants namely citrus pectin, peptone and NaH2PO4 were pointed out by PBD to impose significant consequences (P<0.05) on the process outcome (POS' levels). Optimal levels of these key determinants along with maximal of POS' levels were set by BBD and canonical analysis to be 2.28% (w/v) citrus pectin, 0.026% (w/v) peptone and 0.28% (w/v) NaH2PO4 to achieve a net amount of 1.3 g POS /2.28 g citrus pectin. Through this approach, a yield of 57% (w/w) POS of the total citrus pectin was obtained after 24 h of fungal growth on optimized citrus pectin-based medium. A fold enhancement of 13 times in POS' levels released in the fermentation fungal broth was realized by the end of the optimization strategy. This novel robust approach is considered a new insight towards POS biosynthesis via efficient, rapid and non-cumbersome procedure. To the best of authors' knowledge, the present work is the first article underlining detailed POS production from the fermentation broth of a fungus growing on citrus pectin-based medium.