Ferment Maltose Research Articles

Danielozyma pruni sp. nov., an asexual yeast species isolated from insect frass.

Two strains (NYNU 218101 and NYNU 218104) of an asexual yeast species were isolated from insect frass collected in insect tunnels of red leaf plum trees in the Henan Province, central China. Molecular phylogenetic analysis of the D1/D2 domain of the large subunit rRNA gene and the internal transcribed spacer (ITS) region showed that these two strains belonged to the genus Danielozyma, with Danielozyma litseae as the closest known species. They differed from the type strain of D. litseae by 0.6 % substitutions (three substitutions and one gap) in the D1/D2 domain and by 5.1 % substitutions (19 substitutions and six gaps) in the ITS region, respectively. When compared with the partial ACT1, TEF1 and RPB1 gene sequences, they differed by 3 % (26 substitutions), 2.7 % (25 substitutions) and 9 %(54 substitutions) from D. litseae NRRL YB-3246T in these regions. Physiologically, they also differed from its closest known species D. litseae based on the ability to assimilate inulin and galactitol, as well as to grow in 0.1 % cycloheximide and its inability to ferment maltose and raffinose. In order to classify the two new isolates based on morphological and molecular evidence, we proposed the description of a novel species Danielozyma pruni sp. nov. with strain JCM 35735T as holotype (Mycobank MB 849101).

Toxigenic characterization, spoilage potential, and antimicrobial susceptibility of coagulase-positive Staphylococcus species isolated from Minas Frescal cheese

This study aimed to identify coagulase-positive staphylococci (CPS) species from 21 samples of clandestine Minas Frescal cheese, investigate the potential for deterioration in psychrotrophic and mesophilic conditions, verify the toxigenic potential of Staphylococcus aureus, and determine the antimicrobial susceptibility profile of toxigenic S. aureus. Species determination was performed based on the detection of β-hemolysis in 5% ovine blood agar; fermentation of mannitol, maltose, and trehalose sugars; and production of acetoin. After species determination, DNA extraction and analysis was performed for S. aureus colonies for genes encoding staphylococcal toxins (eta, etb, tst, sea, seb, sec, sed, and see) using 2 multiplex PCR assays. Isolates identified as toxigenic S. aureus were tested for antimicrobial susceptibility to tetracycline, erythromycin, clindamycin, gentamicin, ciprofloxacin, sulfazotrim, trimethoprim, streptomycin, cefoxitin, vancomycin and enrofloxacin. Elevated CPS counts were observed with an average of >6 log cfu/g. Of the 355 isolates, 177 (49.86%) were identified as S. aureus. Staphylococcus hyicus, Staphylococcus intermedius, Staphylococcus delphini, and Staphylococcus coagulans were identified in 3 (0.84%), 2 (0.56%), 2 (0.56%), and 1 (0.28%) isolates, respectively. Of the total number of S. aureus, 25 (52.08%) were positive for the gene that encodes for toxic shock toxin (TSST-1). Another 16 (33.33%) were positive for the sea gene, and 4 isolates (8.33%) were positive for see and one isolate each was positive for seb (2.08%), sec (2.08%), and etb (2.08%) genes. All isolates demonstrated lipolytic activity under mesophilic and psychrotrophic conditions. S. intermedius and S. hyicus had the most prominent proteolytic potential. Multidrug resistance was observed in most of the potentially toxigenic isolates, with clindamycin having the lowest efficiency (40%), whereas the aminoglycosides (gentamicin and streptomycin) had the highest effectiveness demonstrating inhibition in all evaluated isolates. Methicillin-resistant S. aureus (MRSA) was detected. Minas Frescal cheeses, marketed in the north of Tocantins in the Brazilian Amazon region, do not comply with legal quality standards and pose a public health risk due to the enterotoxigenic potential of multiresistant isolates, in addition to low shelf life of the samples given the high spoilage potential of this microbiota.

Bacteroides rhinocerotis sp. nov., isolated from the fresh feces of rhinoceros in Beijing Zoo.

A Gram-negativestrain, anaerobic, non-motile, non-spore-forming, rod-shaped bacterial strain named as NGMCC 1.200684T was isolated from the fresh feces of rhinoceros in Beijing Zoo. Based on 16S rRNA gene sequences, phylogenetic analysis indicated that strain NGMCC 1.200684T belonged to the genus Bacteroides and was most strongly related to the type strain of Bacteroides uniformis ATCC 8492T (96.88%). The G + C content of the genomic DNA was determined to be 46.62%. Between strains NGMCC 1.200684T and B. uniformis ATCC 8492T, the average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) were 93.89 and 67.60%, respectively. Strain NGMCC 1.200684T can produce acid from fermentation of several substrates, including glucose, mannitol, lactose, saccharose, maltose, salicin, xylose, cellobiose, mannose, raffinose, sorbitol, trehalose, D-galactose, and maltotriose. The major cellular fatty acids (> 10%) were identified as anteiso-C15:0, iso-C15:0, iso-C14:0, and iso-C17:0 3-OH. The polar lipid profiles of strain NGMCC 1.200684T were determined to contain diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, three unknown phospholipids, and two unknown amino-phospholipids. Based on phenotypic, phylogenetic, and chemotaxonomic characteristics, a novel species of the genus Bacteroides, Bacteroides rhinocerotis sp. nov. is proposed. The type strain is NGMCC 1.200684T (= CGMCC 1.18013T = JCM 35702T).

Production of a Series of Long-Chain Isomaltooligosaccharides from Maltose by Bacillus subtilis AP-1 and Associated Prebiotic Properties.

Bacillus subtilis strain AP-1, which produces α-glucosidase with transglucosidase activity, was used to produce a series of long-chain isomaltooligosaccharides (IMOs) with degree of polymerization (DP) ranging from 2 to 14 by direct fermentation of maltose. A total IMOs yield of 36.33 g/L without contabacillusmination from glucose and maltose was achieved at 36 h of cultivation using 50 g/L of maltose, with a yield of 72.7%. IMOs were purified by size exclusion chromatography with a Superdex 30 Increase column. The molecular mass and DP of IMOs were analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/MS). Subsequently, linkages in produced oligosaccharides were verified by enzymatic hydrolysis with α-amylase and oligo-α-1,6-glucosidase. These IMOs showed prebiotic properties, namely tolerance to acidic conditions and digestive enzymes of the gastrointestinal tract, stimulation of probiotic bacteria growth to produce short-chain fatty acids and no stimulating effect on pathogenic bacteria growth. Moreover, these IMOs were not toxic to mammalian cells at up to 5 mg/mL, indicating their biocompatibility. Therefore, this research demonstrated a simple and economical method for producing IMOs with DP2-14 without additional operations; moreover, the excellent prebiotic properties of the IMOs offer great prospects for their application in functional foods.

Multilevel System of Studying Plague Microbe Strains Proprties in the Republic of Kazakhstan

The study of freshly isolated cultures is necessary to form an objective idea of the properties of plague microbe natural populations. The analysis of the levels of investigating the properties of strains has been carried out and the characteristics of Yersinia pestis in Kazakhstan are presented. The results of studying the phenotypic and genetic properties of plague microbe natural strains are provided. Following the epizootiological survey of natural plague foci, the museums of live cultures at plague control stations annually receive strains of plague pathogen, which are transferred to the National Collection of Microorganisms of the National Scientific Center of Particularly Dangerous Infections (NSCPDI). One of the main points of Y. pestis strains analysis is the determination of their typicality/atypicality. The study of strains begins at the moment of their isolation by anti-epidemic units. The primary identification of strains is carried out in laboratories of anti-epidemic units by morphology, sensitivity to plague and pseudotuberculosis bacteriophages, fermentation of glycerol, rhamnose and sucrose. In the laboratories of plague control stations and departments, fermentation of maltose and arabinose, denitrification, amino acid requirements, virulence, sensitivity to antibiotics are additionally investigated. Analysis of strains virulence includes determination of calcium dependence, the presence and amount of F1, pesticinogenicity and sensitivity to pesticin 1 and virulence for white mice. The assessment and preservation of the collected gene pool in the NSCPDI National Collection includes various activities, one of the main ones is an in-depth study of all features using standard microbiological methods, molecular methods for complete identification and creation of a data bank containing information about the genome of strains at different intensity of the epizootic process. The NSCPDI has a digital database on the registration and movement of strains, equipment for molecular research. The collection evaluates properties, systematizes information, and ensures the viability of plague pathogen strains for longterm storage.

Non-Conventional Yeast: Behavior under Pure Culture, Sequential and Aeration Conditions in Beer Fermentation.

The use of wild yeasts, isolated from different environments, is becoming the most interesting option for the production of new beers. The objective of this study is to evaluate the potential of seven non-conventional yeast strains from five different species (Saccharomyces cerevisiae, Hanseniaspora guilliermondii, Metschnikowia pulcherrima, Torulaspora delbrueckii, and Zygosaccharomyces bailii) isolated from Madrid agriculture to produce type ale beer. Wild yeast strains were evaluated at laboratory and pilot plant scales under different fermentation conditions (pure, aerated, and sequential culture). Strain S. cerevisiae SafAle S-04 was used as a reference. Throughout the fermentation of beer, volatile compounds were determined by GC and residual sugars by HPLC, among other parameters. The yeast strains used for the fermentation in pure culture conditions were unable to ferment maltose and maltotriose (0.73-1.18% v/v of ethanol). The results of the study under aerated conditions showed varying levels of higher alcohol and ester concentrations. It should be noted that the strain CLI 1057 (S. cerevisiae) fermented maltose in the presence of oxygen (Kluyver effect). This strain also showed a high production of 4-vinyl guaiacol, making it suitable for producing beers with a phenolic profile. Finally, three strains (H. guilliermondii, Z. bailii, and T. delbrueckii) were evaluated in sequential culture together with commercial strain and found to improve the organoleptic characteristics of the brewed beer. These approaches offer the opportunity to add new product characteristics to the beers.

Beyond Saccharomyces pastorianus for modern lager brews: Exploring non-cerevisiae Saccharomyces hybrids with heterotic maltotriose consumption and novel aroma profile.

Non-domesticated, wild Saccharomyces yeasts have promising characteristics for beer diversification, particularly when used in the generation of de novo interspecific hybrids. A major motivation for the current work was the question whether attractive novel Saccharomyces interspecific hybrids can be created for the production of exotic lager beers without using the genomic resources of the ale yeast Saccharomyces cerevisiae. Importantly, maltotriose utilization is an essential characteristic typically associated with domesticated ale/lager brewing strains. A high-throughput screening on nearly 200 strains representing all eight species of the Saccharomyces genus was conducted. Three Saccharomyces mikatae strains were able to aerobically grow on maltotriose as the sole carbon source, a trait until recently unidentified for this species. Our screening also confirmed the recently reported maltotriose utilization of the S. jurei strain D5095T. Remarkably, de novo hybrids between a maltotriose-utilizing S. mikatae or S. jurei strain and the maltotriose-negative Saccharomyces eubayanus strain CBS 12357T displayed heterosis and outperformed both parents with regard to aerobically utilizing maltotriose as the sole source of carbon. Indeed, the maximum specific growth rates on this sugar were comparable to the well-known industrial strain, Saccharomyces pastorianus CBS 1513. In lager brewing settings (oxygen-limited), the new hybrids were able to ferment maltose, while maltotriose was not metabolized. Favorable fruity esters were produced, demonstrating that the novel hybrids have the potential to add to the diversity of lager brewing.

Characterization of wild type yeast isolated from Sabah soil for environmental friendly biofuel production

Biofuel production by utilizing yeast during fermentation process is one of the main concern to maximize the ethanol productivity. In this study, a total of 20 soil examples were collected from 4 sampling site around Kota Kinabalu. They were selected due to their potential habitat of yeast S. cerevisiae. The purpose of this study was to isolate and characterize S. cerevisiae from soil for bioethanol production. A total of 6 strains of yeast were isolated with the use of yeast-extract peptone agar medium. The isolated strains were identified by morphological, physiological and molecular characterization, resulting in discovery of the S. cerevisiae from the samples. In physiological characterization by fermentation of six different carbohydrates showed that the yeast isolates P2A have potential to ferment maltose, glucose and galactose. The strain P2A was evaluated further for their ethanol tolerance capacity. The strain can tolerate up to 12.5% concentration of ethanol. Pure strain of P2A was inoculated in anaerobic conditions with 200 rpm for 48 h at 30°C to be used for ethanol. The concentration of glucose after 72 h of fermentation for P2A was found to be 0.982 mg/mL.

Dark fermentative hydrogen production from simple sugars and various wastewaters by a newly isolated Thermoanaerobacterium thermosaccharolyticum SP-H2

The hydrogen-producing bacterium SP-H2 was isolated from a thermophilic acidogenic reactor inoculated with municipal sewage sludge and processing a carbohydrate-rich simulated food waste. Based on the 16S rRNA gene sequence, the bacterium was identified as Thermoanaerobacterium thermosaccharolyticum. The maximum growth rate was observed at 55–60 °C and pH 7.5. The H2-producing activity of the bacterium was studied using mono-, di- and tri-saccharides related to both hexoses (maltose, glucose, mannose, fructose, lactose, galactose, sucrose, raffinose, cellobiose) and pentoses (xylose and arabinose), as well as using real wastewaters (cheese whey, confectionery wastewater, sugar-beet processing wastewater). The highest H2 yield was observed during dark fermentation (DF) of maltose (1.91 mol H2/mol hexose or 77.8 mmol H2/L). The maximum H2 production rate was observed during DF of xylose (13.3 ml H2/g COD/h) and cellobiose (2.47 mmol H2/L/h). The main soluble metabolite products were acetate, ethanol and butyrate. The acetate concentration had a statistically significant positive correlation with the H2 content in biogas and the specific H2 yield. Based on the results of the correlation analysis, it was tentatively assumed that in the formic acid (mixed-acid) type fermentation, the rate of H2 production was higher than in the butyric acid type fermentation. With regard to real wastewater, cheese whey and confectionery wastewater were distinguished by a higher H2 yield (152 ml H2/g COD) and H2 production rate (0.57 mmol H2/L/h), respectively. The highest concentrations of confectionery wastewater and cheese whey, at which the DF process took place, were 5915 and 7311 mg COD/L, respectively. At the same time, SP-H2 dominated in the microbial community, despite the presence of indigenous microorganisms in wastewater. Thus, T. thermosaccharolyticum SP-H2 is a promising strain for DF of carbohydrate-rich unsterile wastewater under thermophilic conditions.

A Comparative Genomic and Safety Assessment of Six Lactiplantibacillus plantarum subsp. argentoratensis Strains Isolated from Spontaneously Fermented Greek Wheat Sourdoughs for Potential Biotechnological Application.

The comparative genome analysis of six Lactiplantibacillus plantarum subsp. argentoratensis strains previously isolated from spontaneously fermented Greek wheat sourdoughs is presented. Genomic attributes related to food safety have been studied according to the European Food Safety Authority (EFSA) suggestions for the use of lactic acid bacteria (LAB) in the production of foods. Bioinformatic analysis revealed a complete set of genes for maltose, sucrose, glucose, and fructose fermentation; conversion of fructose to mannitol; folate and riboflavin biosynthesis; acetoin production; conversion of citrate to oxaloacetate; and the ability to produce antimicrobial compounds (plantaricins). Pathogenic factors were absent but some antibiotic resistance genes were detected. CRISPR and cas genes were present as well as various mobile genetic elements (MGEs) such as plasmids, prophages, and insertion sequences. The production of biogenic amines by these strains was not possible due to the absence of key genes in their genome except lysine decarboxylase associated with cadaverine; however, potential degradation of these substances was identified due to the presence of a blue copper oxidase precursor and a multicopper oxidase protein family. Finally, comparative genomics and pan-genome analysis showed genetic differences between the strains (e.g., variable pln locus), and it facilitated the identification of various phenotypic and probiotic-related properties.

Performance of wild Saccharomyces and Non‐Saccharomyces yeasts as starter cultures in dough fermentation and bread making

SummaryThe use of wild Saccharomyces and non‐Saccharomyces yeasts might result in bread with different and attractive sensory characteristics. This study aimed to evaluate the performance of Saccharomyces and non‐Saccharomyces yeasts as starter culture in dough fermentation to bread making and the physicochemical parameters and aromatic profile of bread. All 26 wild yeasts strains isolated from Brazilian Cerrado fruit and tree bark were osmotolerant, and 19.4% were able to ferment maltose. Candida tropicalis ART101.3 and Saccharomyces cerevisiae SC5952 had the best growth capacity under high concentrations of glucose and maltose. Also, they were resistant to lyophilisation. Kinetic parameters of bioreactor cultivations showed high cell growth and lower generation time with 10 g L−1 maltose. Bread produced with C. tropicalis ART101.3 and the control bread had similar physicochemical properties and acceptance of consumers. Bread with S. cerevisiae SC5951 had a lower specific volume and a different colour than control bread; however, the consumers found no significant difference. More than 70% of the consumers demonstrated purchase intention of bread produced with both wild yeasts. The present study shows the potential of native Cerrado yeasts to be used and exploited in industrial processes and contributes to the diversification of bread starter cultures.

Identification and selection of a new Saccharomyces cerevisiae strain isolated from Brazilian ethanol fermentation process for application in beer production

The fermented beverage industry is always pursuing alternatives to make products that delight consumers with special or unique characteristics. The identification and improvement of new yeast strains emerge as an opportunity; however, wild strains usually have a limitation in maltose fermentation and/or off-flavors production. Here we report the production of a Blond-style ale beer using a bioethanol isolated strain (LBGA-287) with flavor complexity approved in sensorial panels. LBGA-287 also showed an increase in maltose consumption, growth and fermentation rates when compared to the commercial yeast. Using qPCR analysis, genes related to the (i) efficiency of fermentation (ii) production of aromas/off-flavors, and (iii) metabolization of carbohydrates were found as differentially expressed in the isolated strains when compared to industrial yeast. This suggests that LBGA-287 could have an important impact on beer production, improving brewing efficiency, quality and diversity of this beverage, and most importantly satisfying the final consumer.

Sugar-seeking insects as a source of diverse bread-making yeasts with enhanced attributes.

Insects represent a particularly interesting habitat in which to search for novel yeasts of value to industry. Insect-associated yeasts have the potential to have traits relevant to modern food and beverage production due to insect-yeast interactions, with such traits including diverse carbohydrate metabolisms, high sugar tolerance, and general stress tolerance. Here, we consider the potential value of insect-associated yeasts in the specific context of baking. We isolated 63 yeast strains from 13 species of hymenoptera from the United States, representing 37 yeast species from 14 genera. Screening for the ability to ferment maltose, a sugar important for bread production, resulted in the identification of 13 strains of Candida, Lachancea, and Pichia species. We assessed their ability to leaven dough. All strains produced baked loaves comparable to a commercial baking strain of Saccharomyces cerevisiae. The same 13 strains were also grown under various sugar and salt conditions relevant to osmotic challenges experienced in the manufacturing processes and the production of sweet dough. We show that many of these yeast strains, most notably strains of Lachancea species, grow at a similar or higher rate and population size as commercial baker's yeast. We additionally assessed the comparative phenotypes and genetics of insect-associated S.cerevisiae strains unable to ferment maltose and identified baking-relevant traits, including variations in the HOG1 signaling pathway and diverse carbohydrate metabolisms. Our results suggest that non-conventional yeasts have high potential for baking and, more generally, showcase the success of bioprospecting in insects for identifying yeasts relevant for industrial uses.

Preliminary study for investigation of G. anatis in broilers Abdelazeem M. Algammal1, Wafaa A. Abd El-Ghany2, Amira A. Elewa3, and Ahmed M. Hamouda3

Gallibacterium anatis is recognized as a globally distributed species of bacteria that has been isolated from birds . The aim of the present prelaminary study is to investigate the prevalence of G. anatis isolated from diseased chickens from private commercial broiler farms at Ismailia governorate, Egypt. A total of 80 tracheal swabs obtained from broiler chickens suffering from respiratory manifestations. The collected specimens were subjected to bacteriological examination and the prevalence of G.anatis was 35%. All obtained isolates were positive for oxidase, catalase, nitrate reduction, sucrose, sorbitol, and mannitol fermentation tests. However, the obtained isolates were negative for citrate utilization, indole, urease, gelatinase and maltose fermentation tests. Besides, the recovered isolates were negative for the motility test. The gold standard method of bacterial isolation and identification( including culture characters, hemolytic activity on blood agar, morphological characters, motility test, and biochemical characteristics) is essential for characterization of G. anatis in birds.

Temporal evolution of master regulator Crp identifies pyrimidines as catabolite modulator factors

The evolution of microorganisms often involves changes of unclear relevance, such as transient phenotypes and sequential development of multiple adaptive mutations in hotspot genes. Previously, we showed that ageing colonies of an E. coli mutant unable to produce cAMP when grown on maltose, accumulated mutations in the crp gene (encoding a global transcription factor) and in genes involved in pyrimidine metabolism such as cmk; combined mutations in both crp and cmk enabled fermentation of maltose (which usually requires cAMP-mediated Crp activation for catabolic pathway expression). Here, we study the sequential generation of hotspot mutations in those genes, and uncover a regulatory role of pyrimidine nucleosides in carbon catabolism. Cytidine binds to the cytidine regulator CytR, modifies the expression of sigma factor 32 (RpoH), and thereby impacts global gene expression. In addition, cytidine binds and activates a Crp mutant directly, thus modulating catabolic pathway expression, and could be the catabolite modulating factor whose existence was suggested by Jacques Monod and colleagues in 1976. Therefore, transcription factor Crp appears to work in concert with CytR and RpoH, serving a dual role in sensing both carbon availability and metabolic flux towards DNA and RNA. Our findings show how certain alterations in metabolite concentrations (associated with colony ageing and/or due to mutations in metabolic or regulatory genes) can drive the evolution in non-growing cells.

Prevalence and antimicrobial susceptibility patterns of Vibrio cholerae in dairy excreta

Vibrio cholerae is a major etiological agent of human diarrhoea and has become epidemic across the world in the recent past. A cross-sectional study was conducted to assess the prevalence of V. cholerae from dairy excreta along with antimicrobial resistant status of the isolates. A total 50 samples were collected from 50 different household manure pit located at Bangladesh Agriculture University (BAU) surrounding area, Mymensingh. Alkaline peptone water was used for enrichment of the samples followed by inoculation onto thiosulfate citrate bile salt sucrose (TCBS) agar media for the isolation of Vibrio spp., which were further confirmed via Vibrio genus specific molecular assay. Biochemical tests were performed to identify V. cholerae from the isolates of Vibrio spp. Out of 50 samples 17 (34%) were confirmed as Vibrio spp. as they produced characteristic yellow colonies on TCBS agar and had found to possess recombinase A gene that confirmed the identity of Vibrio spp. From this 17 Vibrio isolates, 6 (12% in total from 50 samples) were identified as V. cholerae based on different biochemical tests. All the isolates fermented glucose, maltose, sucrose and mannitol with the production of only acid. The isolates were positive in oxidase, gelatinase, methyl-red (MR) and indole test, but negative in case of voges-proskaure (VP) test. In antimicrobial susceptibility testing, V. cholerae isolates showed 100% sensitivity to gentamycin, chloramphenicol and tetracycline with moderate sensitivity to ciprofloxacin and co-trimoxazole. A high level of resistance was observed to ampicillin (100%) followed by moderate resistance to erythromycin and imipenem. In the present study about 33.33% (n = 2) of 6 isolated V. cholerae were found to be multidrug resistant (MDR) as they demonstrated resistant against 3 antimicrobial agents. The findings of this study substantiate the presence of MDR V. cholerae in the dairy excreta, which indicates the role of domestic animals to serve as a reservoir that might pose a health risk to human. Hygienic management of animal waste is needed to reduce the burden of human illness.
 Asian Australas. J. Biosci. Biotechnol. 2021, 6 (1), 40-49

Immune Responses Induced in Chickens by Capsular Extract of P. Multocida Isolated From Farm Rat

An experiment was conducted to investigate the immune response induced in chickens by capsular extract of Pasteurella multocida isolated from rats wandering in and around the poultry farms. The rat isolate of P. multocida was isolated and identified by cultural, morphological, and biochemical characteristics, followed by capsular extract preparation and experimental vaccine development. The isolated P. multocida was found Gram-negative, non-motile, non-spore forming rod occurring singly or pains and occasionally as chains or filaments in Gram’s-staining method. The isolates consistently produced acid from dextrose, sucrose and mannitol but not fermented maltose or lactose. The Capsular antigen was extracted and confirmed by acriflavine test. Finally, experimental fowl cholera vaccine was prepared. Primary vaccination was performed at the dose rate of 5.6×107 CFU/ml through intramuscular and subcutaneous routes in birds of group A (10 birds) and group B (10 birds) and group C (10 birds) were control birds. Secondary vaccination was similarly performed after 15 days of primary vaccination in groups A and B. The levels of pre-vaccination and post-vaccination sera were determined by passive haemagglutination test. The passive haemagglutination antibody titre was recorded on 15 and 35 days of post vaccination in groups A and B. It was demonstrated that experimental capsular extract fowl cholera vaccine conferred 100% protection (p<0.01) against challenge infection and found to be safe. It could be suggested that after thorough field trial, the experimentally prepared capsular extract FC vaccine using rat isolate of P. multocida may be used side by side with conventional FC vaccine.
 Res. Agric., Livest. Fish.8(1): 117-124, April 2021

Strain-specific interaction of Fructilactobacillus sanfranciscensis with yeasts in the sourdough fermentation

Fructilactobacillus (F.) sanfranciscensis is a key bacterium in traditional (type 1) sourdough fermentations. It typically occurs in combination with the sourdough yeast Kazachstania (K.) humilis or the generalist Saccharomyces (S.) cerevisiae. Previous studies revealed intra-species diversity in competitiveness or dominance in sourdoughs of F. sanfranciscensis, as well as preferences for a life with or without a specific yeast. In this study representative, differently behaving strains were studied in media with different sugars and electron acceptors, and in rye sourdough fermentations in the presence and absence of K. humilis or S. cerevisiae. Strain-specific differences were observed in sugar and organic acids spectra in media, and in sourdoughs with F. sanfranciscensis strains in combination with K. humilis or S. cerevisiae. F. sanfranciscensis TMW 1.1150 proved dominant in the presence and absence of any yeast because it most effectively used maltose. Its maltose fermentation was unaffected by electron acceptors. F. sanfranciscensis TMW 1.2138 was the weakest maltose fermenter and incapable of glucose fermentation, and evidently not competitive against the other strains. F. sanfranciscensis TMW 1.392 was the most versatile strain regarding the utilization of different carbohydrates and its ability to exploit electron acceptors like fructose and oxygen. In sourdoughs without yeasts, it outcompeted other strains. The metabolism of F. sanfranciscensis TMW 1.907 was stimulated in combination with S. cerevisiae. In competitive trials, it was assertive only with S. cerevisiae. The intra-species differences in carbohydrate metabolism can widely explain the differences in their behavior in sourdough fermentation. Interaction between F. sanfranciscensis and the yeasts was strain specific and supposedly commensal with K. humilis and rather competitive with S. cerevisiae.

Physiological performance of Kazachstania unispora in sourdough environments

In this work we explored the potential of several strains of Kazachstania unispora to be used as non-conventional yeasts in sourdough fermentation. Properties such as carbohydrate source utilization, tolerance to different environmental factors and the performance in fermentation were evaluated. The K. unispora strains are characterized by rather restricted substrate utilization: only glucose and fructose supported the growth of the strains. However, the growth in presence of fructose was higher compared to a Saccharomyces cerevisiae commercial strain. Moreover, the inability to ferment maltose can be considered a positive characteristic in sourdoughs, where the yeasts can form a nutritional mutualism with maltose-positive Lactic Acid Bacteria. Tolerance assays showed that K. unispora strains are adapted to a sourdough environment: they were able to grow in conditions of high osmolarity, high acidity and in presence of organic acids, ethanol and salt. Finally, the performance in fermentation was comparable with the S. cerevisiae commercial strain. Moreover, the growth was more efficient, which is an advantage in obtaining the biomass in an industrial scale. Our data show that K. unispora strains have positive properties that should be explored further in bakery sector.Graphic abstract

Accuracy of different methods for identification of Staphylococcus haemolyticus

Objectives: Staphylococcus haemolyticus is associated with device-related infections in immunocompromised individuals and acts as a reservoir for antibiotic resistance genes. It is also the species with the highest antibiotic resistance rates. However, identification is still difficult in most clinical laboratories. Simplified biochemical tests give variable results while newer methods such as MALDI-TOF MS and automated systems may not be readily available. Aim: To compare the performance of the simplified biochemical scheme, BD-Phoenix automated system, and PCR for nuc gene for the identification of S. haemolyticus with MALDI-TOF MS as the gold standard. Methods: This study included 427 coagulase-negative staphylococci (CoNS) isolates of which 356 were identified as S. haemolyticus and 71 as other species by MALDI-TOF MS. These isolates were subjected to a simplified biochemical scheme using tests like the fermentation of maltose, sucrose, trehalose, mannose, urease, xylose, ornithine, and susceptibility to novobiocin. Conventional PCR targeting the nuc gene and BD-Phoenix were also used for identification. The accuracy of these methods was assessed in comparison with MALDI-TOF MS. Results: The sensitivity and specificity of biochemical tests, BD- Phoenix and nuc PCR were 97.5% and 97.2%: 97.8% and 100%: 100% and 100% respectively. Inaccurate identification was observed for some of the isolates (2.2% by BD- Phoenix and 2.5% by biochemical tests). These isolates were identified as S. haemolyticus by the other methods. Conclusion: Identification of S. haemolyticus by biochemical tests and BD-Phoenix had good accuracy comparable to PCR as well as MALDI-TOF MS. This simplified biochemical scheme can be easily implemented even in laboratories with limited resources. J Microbiol Infect Dis 2021; 11(1):8-14.