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

Statistical bioprocess optimization for enhanced production of a thermo alkalophilic polygalacturonase (PGase) from Pseudomonas sp. 13156349 using solid substrate fermentation (SSF)

In this study, a polygalacturonase (PGase) producing bacterial strain was isolated and identified as Pseudomonas sp. 13159349 from fruit market soils, and TLC analysis confirmed its pectinolytic activity. Additionally, SSF, Plackett-Burman design (PB), and response surface methodology (RSM) were used to optimize the production of this thermostable and alkalophilic PGase. Wheat bran demonstrated the highest activity (60.13 ± 3.39 U/gm) among the various agricultural wastes used as solid substrates. To further enhance the enzyme production, statistical optimization of media components was investigated using the PB design. Among the 11 variables tested, pH (p < 0.0001), inoculum size (p < 0.0001), incubation time (p < 0.0001), and temperature (p < 0.0041) were found to have a positive effect on the production. The interaction and concentration of the selected factors were examined by RSM, which demonstrated the optimal conditions for maximum production (315.65 U/gm) of the enzyme using wheat bran as the solid substrate were pH 10.5, 61-66 h of incubation, and 6-7.5% inoculum size. The model was highly significant, with a p-value of <0.0001, an F-value of 95.33, and a low CV of 2.31. The RSM model was validated by a laboratory-scale experiment showing 30600 ± 400.32 U/100 gm PGase activity. Thus, SSF and the statistical design of media components resulted in a significant 5.2-fold increase in PGase output solely by using agro waste and optimizing the physical parameters, making this a highly cost-effective bioprocess.

Study on coffee quality improvement by self-induced anaerobic fermentation: Microbial diversity and enzymatic activity

The postharvest fermentation process of coffee has rapidly advanced in the last few years due to the search for quality and diversity of sensorial profiles. A new type of fermentation, named self-induced-anaerobic fermentation (SIAF), is a promising process that has been increasingly used. This study aims to evaluate the sensorial improvement of coffee beverages during SIAF and the influence of microorganism's community and enzymatic activity. The SIAF process was conducted in Brazilian farms for up to 8 days. The sensorial quality of coffee was evaluated by Q-graders; the microbial community was identified by the high-throughput sequencing of 16S rRNA and ITS regions; and the enzymatic activity (invertase, polygalacturonase, and endo-β-mannanase) was also investigated. SIAF increased up to 3.8 points in the total score of sensorial evaluation (compared to the non-fermented sample), in addition to presenting more flavor diversity (especially within the fruity and sweetness descriptors). The high-throughput sequencing identified 655 bacterial and 296 fungal species during the three processes. The bacteria Enterobacter sp., Lactobacillus sp., Pantoea sp., and the fungi Cladosporium sp. and Candida sp. were the predominant genera. Fungi that are potential producers of mycotoxin were identified throughout the process, which indicates a risk of contamination since some of them are not degraded in the roasting process. Thirty-one species of microorganisms were described for the first time in coffee fermentation. The microbial community was influenced by the place where the process was carried out, mainly in relation to the diversity of fungi. Washing the coffee fruits before fermenting led to a fast reduction of pH; a fast development of Lactobacillus sp. and a fast dominance of Candida sp.; a reduction of the fermentation time necessary to achieve the best sensorial score; an increase in the invertase activity in the seed; a more expressive invertase activity in the husk; and a decreasing trend in polygalacturonase activity in the coffee husk. The increase in endo-β-mannanase activity suggests that coffee starts germinating during the process. SIAF has a huge potential to increase the quality and add value to coffee, but further studies must be conducted to access its safety. The study allowed a better knowledge of the spontaneous microbial community and the enzymes that were present in the fermentation process.

Screening of a high-yield strain of avermectin B1a by colony analysis in situ

Avermectin, an agricultural antibiotic, is widely used as an agricultural insecticide and an important lead compound of antibiotics. It is manufactured by Streptomyces avermitilis through fermentation. Manufacturers pay special attention to screening for strains with high fermentation capacity based on morphological properties of the colony and by the result of shake flask fermentation. These traditional screening methods are time-consuming and labor-intensive and require specialized equipment. Moreover, evaluation of colony appearance is highly subjective. To improve and accelerate the screening process, we developed a rapid in situ screening method. Forty-four strains isolated naturally from the spores of industrial high-yielding strains were studied. The data show that the colony fermentation titer is highly correlated with the yield from the shake flask fermentation of avermectin, and the Pearson's R is 0.990. The total titer of avermectins by shake flask fermentation is also highly correlated with the B_1a titer (Pearson's R is 0.994). This result also shows that strains can be quickly screened by analyzing the colony titer. Pigment rings of the colonies that appeared after growing and maturing on the new medium plate were analyzed. The chosen colonies were directly marked and punched and then extracted with methanol. The fermentation ability can be evaluated by measuring the absorbance at 245 nm. This methodology can be applied in both natural breeding and mutation breeding conditions. By continuously breeding from 2008 to 2020, the flask titer of avermectin B_1a increased from 4582 ± 483 to 9197 ± 1134 μg/mL.

Effect of Warm-Water Retting Pretreatment on the Physical Properties of Banana Stem and Its Fibre

In this paper, warm-water flax retting was used as a pretreatment method for banana-fibre extraction. To determine the optimum conditions for flax retting, the physical properties of various parts of stems and fibres in the process of flax retting were analysed. By studying the tensile strength, elongation at break, diameter, moisture regain, and other characteristics of the fibres, the influences of bacteria and enzymes in the retting liquor on the fibre characteristics in different retting stages were determined. Through mechanical-property tests and microscopic observation of the stem skin, the change rules of the mechanical properties and degumming state of the stems were examined. The results showed that the fibre tensile strength of banana stems reached the maximum value of 45 ± 16 cN·tex^-1 after 11 days of retting. As most resins had not been hydrolysed, fibre extraction was difficult. After 21-25 days of retting, the tensile strength of fibres was about 34 ± 10 cN·tex^-1, elongation at break was about 1.71%, and moisture regain was about 13.56%. The fibre characteristics met the process requirements, and the tensile separation stress of the stem was small, about 0.034 MPa. This time point could be used as the optimum endpoint for retting flax in warm water, which could provide theoretical support and research basis for the recycling of banana straw. The functional groups of the extracted fibres were studied by FTIR, which confirmed the observed change rule of each component during degumming. The experimental results showed that a longer retting time corresponded with a lower content of fibre impurities, more thorough degumming, and less difficult extraction; however, strength and toughness decreased.

Comparison of the Endophytic Bacterial Microbiota of Asymptomatic and Symptomatic Ginger Rhizomes During the Activation of Adventitious Bud Development

Bacterial infections are the cause of rhizome rot in ginger (Zingiber officinale). Key members of the endophytic microbial community in ginger rhizomes have not been identified, and their impact on the decay of rhizomes during the activation of adventitious bud development has not been investigated. High-throughput, 16S rRNA amplicon sequencing and inoculation experiments were used to analyze the microbial diversity, community structure and composition, and pathogenicity of isolated bacteria. Our results indicated that the composition of the endophytic microbiota underwent a shift during the progression of rhizome rot disease. Enterobacteriaceae, Lachnospiraceae, and the bacterial genera Clostridium, Bacteroides, Acrobacter, Dysgonomonas, Anaerosinus, Pectobacterium, and Lactococcus were relatively abundant in the bacterial community of rhizomes exhibiting bacterial decay symptoms but were also present in asymptomatic rhizomes. The presence of Enterobacteriaceae and Pseudomonadaceae were positively correlated (ρ = 0.83) at the beginning of the sampling period in the symptomatic group, while a positive correlation (ρ = 0.89) was only observed after 20 days in the asymptomatic group. These data indicate that the co-occurrence of Enterobacteriaceae and Pseudomonadaceae may be associated with the development of ginger rot. Bacterial taxa isolated from ginger rhizomes, such as Enterobacter cloacae, E. hormaechei, and Pseudomonas putida, induced obvious rot symptoms when they were inoculated on ginger rhizomes. Notably, antibiotic-producing bacterial taxa in the Streptococcaceae and Flavobacteriaceae were also relatively abundant in rhizomes with rot and appeared to be linked to the onset of rhizome rot disease. Our results provide important information on the establishment and management of disease in ginger rhizomes.

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.

New insights in pectinase production development and industrial applications

Pectinase, a group of pectin degrading enzymes, is one of the most influential industrial enzymes, helpful in producing a wide variety of products with good qualities. These enzymes are biocatalysts and are highly specific, non-toxic, sustainable, and eco-friendly. Consequently, both pectin and pectinase are crucially essential biomolecules with extensive applicatory perception in the biotechnological sector. The market demand and application of pectinases in new sectors are continuously increasing. However, due to the high cost of the substrate used for the growth of microbes, the production of pectinase using microorganisms is limited. Therefore, low-cost or no-cost substrates, such as various agricultural biomasses, are emphasized in producing pectinases. The importance and implications of pectinases are rising in diverse areas, including bioethanol production, extraction of DNA, and protoplast isolation from a plant. Therefore, this review briefly describes the structure of pectin, types and source of pectinases, substrates and strategies used for pectinases production, and emphasizes diverse potential applications of pectinases. The review also has included a list of pectinases producing microbes and alternative substrates for commercial production of pectinase applicable in pectinase-based industrial technology.Key points• Pectinase applications are continuously expanding.• Organic wastes can be used as low-cost sources of pectin.• Utilization of wastes helps to reduce pollution.

Optimization of substrate composition for pectinase production from Satkara (Citrus macroptera) peel using Aspergillus niger-ATCC 1640 in solid-state fermentation

Pectinase is an enzyme having a broad industrial and commercial application. However, higher production costs may be the major constraint for the wide-scale application of pectinase. Therefore, researchers are trying to reduce the pectinase production cost for subsequent application in the industrial processes by using a unique substrate and optimizing the fermentation medium components and process conditions. The main purpose of the current study was to optimize medium composition for pectinase production using Aspergillus niger-ATCC 1640 in the solid-state fermentation. The Response Surface Methodology (RSM) was performed to evaluate the effects of variables, specifically the concentrations of Satkara peel, urea, (NH₄)₂PO₄, NH₄NO₃, KH₂PO₄, ZnSO₄, and MgSO₄.7H₂O on pectinase production in the solid substrate. Firstly, a two-factorial design, Plackett-Burman design (PBD) was applied to screen the variables that significantly influenced the pectinase production. After finding the critical variables, 15 experimental runs were carried out using a Box-Behnken design (BBD) to derive a statistical model for optimizing the concentrations of the selected variables. The PBD model revealed that Satkara peel, urea, and (NH₄)₂SO₄ significantly affected the pectinase production. RSM results indicated that the predicted response for pectinase production was in good agreement with experimental data (R² = 0.9836). Under the optimized condition of Satkara peel (8.4 g/L), urea (0.5 g/L), and (NH₄)₂SO4 (2.7 g/L), the pectinase activity was predicted to be 0.6178 μmol/mL. In the present study, the experimental pectinase production achieved 0.6045 μmol/mL. The study revealed that optimization through RSM could improve the pectinase production from Satkara peel.

Conversion of Pectin-Containing By-Products to Pectinases by Bacillus amyloliquefaciens and Its Applications on Hydrolyzing Banana Peels for Prebiotics Production

The utilization of pectin-containing by-products may be useful in a variety of fields. This study aims to establish the processing of pectin-containing by-products to produce pectinases using Bacillus amyloliquefaciens TKU050 strain. In this study, several kinds of agricultural pectin-containing by-products from banana (banana peel), rice (rice bran), orange (orange peel), coffee (spent coffee grounds), and wheat (wheat bran) were utilized to provide carbon sources for the production of a pectinase by B. amyloliquefaciens TKU050. B. amyloliquefaciens TKU050 expressed the highest pectinase productivity (0.76 U/mL) on 0.5% wheat bran-containing medium at 37°C for four days. A 58 kDa pectinase was purified from the four-day cultured medium fermented under optimized culture conditions with 7.24% of a recovery ratio and 0.51 U/mg of specific activity, respectively. The optimum temperature, optimum pH, thermal stability, and pH stability of the TKU050 pectinase were 50 °C, pH 6, <50 °C, and pH 6–9, respectively. The TKU050 pectinase was inhibited by sodium dodecyl sulfate and Cu²⁺. The reducing sugar obtained by hydrolyzing banana peel with TKU050 pectinase showed the growth-enhancing effect on the growth of four tested lactic acid bacteria.

Vibrational Spectroscopic Analyses and Imaging of the Early Middle Ages Hemp Bast Fibres Recovered from Lake Sediments

Fourier Transform Infrared (FT-IR) spectroscopy and imaging combined with hierarchical cluster analysis (HCA) was applied to analyse biochemical properties of Early Middle Ages hemp (Cannabis sativa L.) bast fibres collected from lake bottom sediment of lake Słone. The examined plant macrofossil material constitutes residues of the hemp retting process that took place in the 7th–8th century. By comparison of three samples: untreated isolated bast fibres, and fibres incubated overnight at 4 and 37 °C, we were able to mimic the retting conditions. Using FT-IR qualitative and semi-quantitative assessment of the primary polysaccharides content, total protein content, and their spatial distribution was performed within the hemp fibres. The concentration of cellulose remained vastly unchanged, while the concentration of lignin and pectin was the highest in the untreated sample. The spatial distributions of compounds were heterogeneous in the untreated and 4 °C-incubated samples, and homogenous in the specimen processed at 37 °C. Interestingly, a higher amide content was detected in the latter sample indicating the highest degree of enzymatic degradation. In this study, we show that the spectroscopic methods allow for a non-destructive evaluation of biochemical composition of plant fibres without preparation, which can be an appropriate approach for studying ancient plant remains.