Functional Properties of Pediococcus Species Isolated from Traditional Fermented Cereal Gruel and Milk in Nigeria

Pediococcus species were isolated from ogi, fermented cow and sheep milk. Functional properties such as hydrogen peroxide production, tolerance to simulated gastric transit with pepsin and bile salts, bile salt hydrolytic (BSH) activity, in vitro adherence assay and antimicrobial characteristics were carried out. The strains tolerated bile salts and BSH activity was positive. Pediococcus acidilactici OB4 survived gastric transit after 180min comparable to a probiotic strain, L. acidophilus CNRZ1923. The strains exhibited good adhesion to the three extracellular matrices. Two isolates (P. acidilactici OB4 and P. pentosaceus SM3) produced bacteriocin. Bacteriocins were stable at pH 4-9 and on treatment with lipase, catalase, α-amylase and lysozyme, while their activity was lost on treatment with proteinase K, pronase E, pepsin and trypsin. The bacteriocins produced by P. pentosaceus SM3 was heat stable at 100°C for 10 min while P. acidilactici OB4 was stable at 100°C for 30 min. The bacteriocin produced by P. acidilactici OB4 was identified as PedA while P. pentosaceus SM3 was PedB. The bacteriocins had relative heat stability, high anti-listerial activity and a good spectrum of activity against some pathogenic microorganisms. The results demonstrated possible inclusion in a starter culture fermentation process of food and dairy products and safety characteristics.     

Improving the textural properties of an acid-coagulated (Karish) cheese using exopolysaccharide producing cultures

Exopolysaccharide (EPS)-producing Streptococcus thermophilus (CHCC 3534) or its EPS-negative genetic variant S. thermophilus (CHCC 5842) was combined with Lactobacillus delbrueckii ssp bulgaricus (CHCC 769) and used to manufacture Karish cheese to determine the effect of EPS production on the composition, sensory and textural characteristics. Moisture and yield were about 2% higher in cheese made using EPS-producing culture than that made using the EPS-negative mutant. Texture profile analysis showed that the textural characteristics (hardness, consistency, adhesivness, chewiness, relaxation and modulus) were significantly lower in cheese made using EPS-producing culture while cheese made using EPS-negative mutant was significantly lower in cohesiveness. Sensory analysis confirmed the ability of EPS-producing culture to improve Karish cheese texture, as it received higher body and texture scores after aging for 7 and 15 days.     

Physicochemical,rheological and sensory properties of Egyptian Kariesh cheese containing wheat bran

The physicochemical, rheological and sensory properties during the storage of Kariesh cheeses made with 0.1, 0.2, 0.3, 0.4 or 0.5 g wheat bran/100 g milk were evaluated at 0, 7 and 15 days. The cheeses with 0.5 g wheat bran/100 g milk had a significantly (P < 0.01) higher yield and moisture content, and lower pH and protein content than the control. No significant differences (P > 0.01) in salt and ash contents were observed among the cheeses studied. Texture profile analysis showed that the rheological characteristics decreased significantly in cheeses made with wheat bran. These results suggested that wheat bran (up to 0.4%) can be used to produce a fibre fortified Kariesh cheese.     

Characterization and antimicrobial activity of Pediococcus species isolated from South African farm-style cheese

Pediococci are part of the non-starter lactic acid bacteria, LAB, contributing towards cheese ripening. This study was aimed at isolating, characterizing and evaluating the antimicrobial activity of Pediococcus species occurring among commercial and farm-style cheese. Logarithmic counts of LAB ranged from 6.9 to 9.4 cfu/g. Microscopic examination identified 110 (18%) of 606 isolates as presumptive pediococci distributed among farm-style cheese (pasteurized Gouda, young and matured; un-pasteurized aged Bouquet, aged and matured Gouda), in numbers of 33, 21, 28, 12 and 16, respectively. Pediococci were absent in commercial Cheddar cheese. Characterization of pediococci identified 49 Pediococcus acidilactici and 61 Pediococcus pentosaceus isolates. Fifty-two isolates from both species, 27 (24%) P. acidilactici and 25 (23%) P. pentosaceus, inhibited Lactococcus lactis NCDO 176 through the action of pediocins. Among these isolates, seven (6%) P. acidilactici and six (7%) P. pentosaceus inhibited Bacillus cereus ATCC 1178 while 17 (15%) P. acidilactici and 20 (18%) P. pentosaceus inhibited Listeria monocytogenes ATCC 7644. Inhibition levels were variable against L. monocytogenes ATCC 7644 and low against B. cereus ATCC 1178. Both Pediococcus species showed similar inhibition patterns; however, more isolates of P. pentosaceus inhibited L. lactis NCDO 176 and L. monocytogenes ATCC 7644 compared to P. acidilactici.     

Production of nitric oxide (NO) by lactic acid bacteria isolated from fermented products

In this study, the bacteria which were isolated from various milk and fermented food products were tested for their ability to convert metmyoglobin to nitrosomyoglobin. Lactic acid bacteria were isolated from samples of raw milk, unsalted butter, Beyaz cheese, yoghurt, pickles and silage. The nitric oxide (NO) forming abilities of 1534 isolates were tested using plates of de Man, Rogosa, Sharpe agar supplemented with metmyoglobin (MRS-Mb). Ten isolates formed bright red colonies, brown or clear zones due to the conversion of metmyoglobin to nitrosomyoglobin were identified. Five of the 10 bacteria were identified as Lactobacillus plantarum, three as Pediococcus acidilactici, and two as Leuconostoc mesenteroides subsp. dextranicum. NO formation ability was measured in MRS-Mb broth. There were differences not only among the species, but also among the strains of a species. The highest NO concentrations of 51.5, 51.3, 50.2 μM were produced by P. acidilactici S2, L. plantarum T119, and P. acidilactici S3, respectively.     

Influence of exopolysaccharide‐producing cultures on the volatile profile and sensory quality of low‐fat Tulum cheese during ripening

The objective of this investigation was to compare the composition and changes in the concentration of volatiles in low‐fat and full‐fat Tulum cheeses during ripening. Tulum cheese was manufactured from low‐ or full‐fat milk using exopolysaccharide (EPS)‐producing or non‐EPS‐producing starter cultures. A total of 82 volatile compounds were identified belonging to the following chemical groups: acids (seven), esters (21), ketones (14), aldehydes (six), alcohols (14) and miscellaneous compounds (20). The relative amounts of acids, alcohols and aldehydes increased in the cheeses made with EPS‐producing cultures during 90 days of ripening. Differences were found in the volatile profile of full‐fat Tulum cheese compared with the low‐fat variant, especially after 90 days of ripening. Exopolysaccharide‐producing cultures changed the volatile profile, and the EPS‐producing cultures including Streptococcus thermophilus + Lactobacillus delbrueckii subsp. bulgaricus + Lactobacillus helveticus (LF‐EPS2) produced cheese with higher levels of methyl ketones and aldehydes than the non‐EPS cultures. In the sensory analysis, full‐fat Tulum cheeses and the cheese produced with the EPS‐producing culture containing Lb. helveticus (LF‐EPS2) were preferred by the expert panel. It was concluded that the use of EPS‐producing starter cultures in the manufacture of low‐fat Tulum cheese had the potential to improve the flavour.     

Formation of alanine, α-aminobutyrate,acetate, and 2-butanol during cheese ripening by Pediococcus acidilactici FAM18098

There is limited information about the contribution of Pediococcus acidilactici, a nonstarter lactic acid bacteria, to cheese ripening and flavour development. Model Tilsit-type and Gruyère-type cheeses were produced using P. acidilactici FAM18098 as an adjunct. The adjunct did not influence the cheese manufacturing processes. The pediococcal log counts ranged from 7.0 to 8.0 cfu g⁻¹ after 90 and 120 days of ripening. P. acidilactici produced ornithine, a result of arginine metabolism by the arginine deiminase pathway, and α-aminobutyrate and alanine while simultaneously metabolising serine and threonine. The analysis of the volatile compounds in the cheeses showed that higher acetate, 2-butanone, and 2-butanol levels and lower diacetyl levels were present in the cheeses produced with P. acidilactici than in the control cheeses. The study illustrates that P. acidilactici can influence amino acid metabolism in cheese; further, ornithine, α-aminobutyrate, and acetate can serve as indicators for the presence of this species.     

Ripening time estimation of Kariesh cheese

Kariesh cheese is a popular cheese in Egypt produced by acid coagulation of milk. It can be consumed fresh or after ripening. Proteolysis in cheese was measured by determining soluble nitrogen (SN), amino acid nitrogen (AAN), total amino acids (TAA) and free amino acids (FAA). SN, AAN and FAA increased during ripening. Free amino acids profile revealed in total 16 amino acids and the same distribution of free amino acids. Cheese ripening was influenced by the type of milk and the method of production. The mildly acid sweet flavour was attributed to the concentration of glutamic acid, aspartic acid, proline and valine. Linear regression analysis was carried out to estimate the ripening time of this cheese. A positive correlation between the accumulation of amino acid and ripening time was established. The highest coefficient of determination near one resulted from glutamic acid (R² = 0.99) followed by lysine (R² = 0.97–0.99), then aspartic acid (0.90–0.98). From the linear regression equation for glutamic acid, lysine, aspartic acid or proline, the ripening time of Kariesh cheese in weeks was determined as follows: Time of ripening [weeks] = mg amino acid 100 g cheese-a/b where b = slope and a = intercept of regression straight line at 0 time.     

Viability of Salmonella enterica subsp. enterica during the preparation and cold storage of Egyptian soft cheeses and ice-cream

Changes occurring in the viability of Salmonella enterica subsp. enterica during the preparation and cold storage of Domiati cheese, Kariesh cheese and ice-cream were examined. A significant decrease in numbers was observed after whey drainage during the manufacture of Domiati cheese, but Salmonella remained viable for 13 weeks in cheeses prepared from milks with between 60 and 100 g/L NaCl; the viability declined in Domiati cheese made from highly salted milk during the later stages of storage. The method of coagulation used in the preparation of Kariesh cheese affected the survival time of the pathogen, and it varied from 2 to 3 weeks in cheeses made with a slow-acid coagulation method to 4–5 weeks for an acid-rennet coagulation method. This difference was attributed to the higher salt-in-moisture levels and lower pH values of Kariesh cheese prepared by the slow-acid coagulation method. A slight decrease in the numbers of Salmonella resulted from ageing ice-cream mix for 24 h at 0°C, but a greater reduction was evident after one day of frozen storage at −20°C. The pathogen survived further frozen storage for four months without any substantial change in numbers.     

Production of 3-phenyllactic acid and 4-hydroxyphenyllactic acid by Pediococcus acidilactici DSM 20284 fermentation

It was reported that 3-phenyllactic acid (PLA) and 4-hydroxyphenyllactic acid (HPLA) could be produced by Pediococcus acidilactici DSM 20284. PLA and HPLA concentrations were 0.65 and 0.25 mM when P. acidilactici DSM 20284 was grown in MRS broth for 36 h. In comparison with P. acidilactici DSM 20284 fermentation using MRS medium alone, PLA and HPLA production could be significantly promoted by the supplement of the corresponding amino acid (phenylalanine and tyrosine) and ketoacid (phenylpyruvic acid and 4-hydroxyphenylpyruvic acid) precursors in MRS broth, but inhibited by the supplement of the non-corresponding precursors. Promotion and inhibitory effects were both strengthened when supplement amounts increased. Ketoacids precursors showed more promotion effect on the corresponding 2-hydroxy acids production than amino acid precursors; however, amino acid precursors showed more inhibitory effect on non-corresponding 2-hydroxy acids production than ketoacids precursors.     

The effect of using an exopolysaccharide‐producing culture on the physicochemical properties of low‐fat and reduced‐fat Kasar cheeses

A mixed starter culture containing exopolysaccharide (EPS)‐producing strains of Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus was combined with Lactobacillus helveticus LH301 and used in the manufacture of low‐fat and reduced‐fat Kasar cheeses. For comparison, low‐fat (C10) and reduced‐fat (C20) cheeses were made using EPS‐producing (EPS⁺) starter strain and EPS‐non‐producing (EPS^?) starter strain. The physicochemical properties of the cheeses were assessed in terms of chemical composition, texture, microstructure and microbial content over 90 days. Cheeses made with EPS‐producing culture (EPS10 and EPS20) had lower protein contents than control cheeses with 10% and 20% fat in dry basis (C10 and C20). Scanning electron microscopy images showed that using EPS‐producing culture resulted in a less compact protein matrix and sponge‐like structure in the cheese samples. In general, cheeses made using EPS‐producing culture had lower total viable counts. This could be related to the reduced survivability of EPS‐producing cells in the cheese matrix during ripening due to autolysis ability.     

Biological acidification and beer quality: addition of lactic acid bacteria isolated from malt

Two lactic acid bacteria, Pediococcus acidilactici HW01 and Leuconostoc citreum isolated from Pilsner malt, were added during mashing and the impact on fermentation examined. The pH of lactic acid bacteria supplemented (bioacidified) wort and finished beer were lower than that of the control. Bioacidified worts resulted in higher levels of free amino nitrogen, reducing sugars and alcohol in the corresponding beers. Foam stability of beers from P. acidilactici and L. citreum worts were increased by 19% and 26%, respectively. The filtration time was reduced in P. acidilactici treated beers but increased with L. citreum. The use of P. acidilactici and L. citreum as bioacidification agents resulted in beers with higher sensory quality. © 2020 The Institute of Brewing & Distilling     

Influence of pH on the Formation of Glucan by Lactobacillus reuteri TMW 1.106 Exerting a Protective Function Against Extreme pH Values

Lactobacillus reuteri TMW 1.106, a dominant type II sourdough bacterium, produces glucan from sucrose in vitro and in situ. Exopolysaccharides positively affect the texture and mouth feel of foods and their in situ production in fermented foods could be an alternative to the addition of hydrocolloids from plants or non-GRAS microorganisms. The aim of this study was to elucidate a probable function of the EPS for the bacterium. Lb. reuteri TMW 1.106 harbors two glucosyltransferases, Gtf106A and Gtf106B and produces a dextran. Gtf106B exhibited hydrolysis but no transferase activity. Enzymatic production of dextran with the heterologously expressed, N-terminally truncated ΔN Gtf106A was highest at a pH of 4.0, whereas dextran formation in pH static fermentations was optimal between pH 4.7 and 5.4. The dextran synthesised at these pH values had the highest molecular mass (1.2 × 10⁷) and 15% α–(1–4) linkages. A protective effect of this EPS on Lb. reuteri TMW 1.106 against low pH, explaining the low pH-production maximum, could be demonstrated through the delay of cell death.     

Bioconversion of agro‐industrial by‐products to lactic acid using Lactobacillus sakei and two Pediococcus spp. strains

The aim of this study was to evaluate the bioconversion efficiency of rich in cellulose agro‐industrial by‐products such as wheat bran (WB), spent distiller's grain with solids (DGS), brewer's spent grain (BSG) and lupin (Lupinus angustifolius L.) wholemeal fraction (LF) to lactic acid (LA) using acid tolerant lactic acid bacteria (LAB) strains Lactobacillus sakei KTU05‐06, Pediococcus acidilactici KTU05‐7 and P. pentosaceus KTU05‐9. Carbohydrase preparation Depol^? 692L was used for the hydrolysis of non‐starch polysaccharides. Analysed raw materials were suitable substrates for LAB propagation and L‐lactic acid production. The lowest pH (3.6) was found in LF medium after 48 h fermentation with P. acidilactici and P. pentosaceus strains. The lowest pH (3.86) was measured in WB fermented with L. sakei, and in DGS and BSG (pH 3.8 and 3.9 respectively) fermented with P. acidilactici. The highest endoxylanase activity was excreted by the P. acidilactici and P. pentosaceus (84 and 69 XU g^?1 respectively), and the highest α‐amylase activity was of L. sakei (255.6 AU g^?1) after 24 h incubation in WB medium. The L‐lactic acid concentration of 86.11 g kg^?1 was reached after the bioconversion of hydrolysed WB in combination with 48 h fermentation by P. pentosaceus KTU05‐9 strain. LA contents between 222 and 282 mg kg^?1 was produced from lupin processing residues via fermentation using P. acidilactici and P. pentosaceus KTU05‐9 strains. The major challenge within the presented study is the viability of tested LAB in cereal waste media and effective LA production at a low pH (3.6–3.8).     

Nonstarter lactic acid bacteria biofilms and calcium lactate crystals in Cheddar cheese

A sanitized cheese plant was swabbed for the presence of nonstarter lactic acid bacteria (NSLAB) biofilms. Swabs were analyzed to determine the sources and microorganisms responsible for contamination. In pilot plant experiments, cheese vats filled with standard cheese milk (lactose:protein = 1.47) and ultrafiltered cheese milk (lactose:protein = 1.23) were inoculated with Lactococcus lactis ssp. cremoris starter culture (8 log cfu/mL) with or without Lactobacillus curvatus or Pediococci acidilactici as adjunct cultures (2 log cfu/mL). Cheddar cheeses were aged at 7.2 or 10°C for 168 d. The raw milk silo, ultrafiltration unit, cheddaring belt, and cheese tower had NSLAB biofilms ranging from 2 to 4 log cfu/100 cm². The population of Lb. curvatus reached 8 log cfu/g, whereas P. acidilactici reached 7 log cfu/g of experimental Cheddar cheese in 14 d. Higher NSLAB counts were observed in the first 14 d of aging in cheese stored at 10°C compared with that stored at 7.2°C. However, microbial counts decreased more quickly in Cheddar cheeses aged at 10°C compared with 7.2°C after 28 d. In cheeses without specific adjunct cultures (Lb. curvatus or P. acidilactici), calcium lactate crystals were not observed within 168 d. However, crystals were observed after only 56 d in cheeses containing Lb. curvatus, which also had increased concentration of d(−)-lactic acid compared with control cheeses. Our research shows that low levels of contamination with certain NSLAB can result in calcium lactate crystals, regardless of lactose:protein ratio.     

Development of a dairy-based exopolysaccharide bioingredient

An exopolysaccharide (EPS)-producing Streptococcus thermophilus was used to develop an “all-dairy” ingredient with increased EPS content and greater functionality for dairy applications such as Mozzarella cheese. In laboratory-scale trials, milk protein hydrolysate (MPH), whey protein isolate (WPI) and whey protein hydrolysate (WPH) in reconstituted low-heat skim milk powder (LHSMP) were examined as additional dairy protein sources to increase the production of EPS. WPH supplementation resulted in the greatest EPS production. In batch fermentation, a medium based on LHSMP and WPH, combined with optimum conditions of temperature and pH, was used to obtain maximum production of EPS from S. thermophilus. EPS production was growth associated. The fermented biomass was harvested at the end of the exponential phase and freeze-dried. The reduced viable cell count and the retention of ropiness of the powder from the drying process enabled a higher level of EPS inoculation in a preliminary Mozzarella cheese manufacturing trial.     

Starter Culture and Time/Temperature of Storage Influences on Quality of Fermented Mutton Sausage

Rate of acid production and ability to produce antimicrobial activity were tested on P. acidilactici H and L. plantarum 27 during growth in a sausage formula mixture. Lactacel 75 was used as control. Starter culture did not affect water activity, pH, ash or protein content, fatty acid composition (except for nonadecanoate), cholesterol content or retention of moisture, protein, fat, ash or fatty acids. Sausages made with P. acidilactici H had the lowest (P<0.05) retention (89.6%) of cholesterol during processing and storage. Sensory evaluation of fermented sausage and bologna prepared from the two starter cultures or from Lactacel 75 indicated both products were acceptable after 50–60 days storage at 4°C.     

Application of ruthenium red and colloidal gold-labeled lectin for the visualization of bacterial exopolysaccharides in Cheddar cheese matrix using transmission electron microscopy

The objective of the present study was to develop a methodology for direct observation of capsular and ropy strains and their exopolysaccharides (EPS) in a Cheddar cheese matrix. Cheddar cheeses with 50% reduced fat were made from milk containing 1.7% fat using mixed starter culture containing either capsule-forming Lactococcus lactis subsp. cremoris (SMQ-461) or ropy L. lactis subsp. cremoris (JRF-1) strains. Control cheese was made using the EPS-negative L. lactis subsp. cremoris (RBL132) strain. Following cheese pressing, samples were taken from each cheese treatment and examined by transmission electron microscopy (TEM). Samples were divided into two series: the first was prepared following the conventional methods (involving fixation, post fixation, dehydration and embedding in resin) and the second with added ruthenium red at 0.15% (w/v) during the fixation, post fixation and washing procedures. Gold-labeled lectin was also used for the visualization and localization of EPS in cheese matrix. Electron micrographs showed that ruthenium red makes it possible to visualize and enhance the resolution of the EPS in a Cheddar matrix compared with the conventional method. The EPS layer of the capsular strain appeared regular and evenly distributed around the cell, whereas the cell-associated EPS layer produced by the ropy strain was longer, more irregular (having a filamentous structure) and unevenly surrounded the cell. EPS released from the ropy strain appeared to form a network-like structure located principally in whey pockets and appeared to interact with the casein matrix and fat globule membrane. Labeling EPS by lectin conjugated to colloidal gold could only be performed with conventional preparation of cheese samples and appeared to react only with the cell surface rather than with liberated EPS. Besides their ability to bind water and increase cheese yield, capsular and ropy strains used in this study appear to have potential autolytic characteristics, which may have an impact on cheese proteolysis, texture and flavor quality.     

Diversity and dynamic of lactic acid bacteria strains during aging of a long ripened hard cheese produced from raw milk and undefined natural starter

The aim of this study was to explore diversity and dynamic of indigenous LAB strains associated with a long ripened hard cheese produced from raw milk and undefined natural starter such as PDO Grana Padano cheese. Samples of milk, curd, natural whey culture and cheeses (2nd, 6th, 9th and 13th months of ripening) were collected from 6 cheese factories in northern Italy. DNA was extracted from each sample and from 194 LAB isolates. tRNA^Ala-23S rDNA-RFLP was applied to identify isolates. Strain diversity was assessed by (GTG)5 rep-PCR and RAPD(P1)-PCR. Finally, culture-independent LH-PCR (V1–V2 16S-rDNA), was considered to explore structure and dynamic of the microbiota. Grana Padano LAB were represented mainly by Lactobacillus rhamnosus, Lactobacillus casei, Lactobacillus paracasei, Lactobacillus delbrueckii, Lactobacillus helveticus and Pediococcus acidilactici, while the structure and dynamic of microbiota at different localities was specific. The strength of this work is to have focused the study on isolates coming from more than one cheese factories rather than a high number of isolates from one unique production. We provided a valuable insight into inter and intraspecies diversity of typical LAB strains during ripening of traditional PDO Grana Padano, contributing to the understanding of specific microbial ecosystem of this cheese.     

Productions and monomer compositions of exopolysaccharides by Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus strains isolated from traditional home-made yoghurts and raw milk

In this study, a total of forty‐five strains of lactobacilli and streptococci were determined exopolysaccharide (EPS) production in skim milk and Man Rogosa and Sharpe (MRS)/M17 medium, viscosity and proteolytic activity. The exopolysaccharide production by lactobacilli strains during growth in MRS medium was twenty‐one to 211 mg L^?1, while in skim milk was to thirty‐six to 315 mg L^?1. The EPS production by streptococci strains during growth in M17 medium was sixteen to 114 mg L^?1, while in skim milk was to twenty‐four to 140 mg L^?1. The EPS production of strains was lower in MRS/M17 medium than skim milk. Results showed that it was not clear correlation between the viscosity and EPS production of some strains. All strains were shown proteolytic activity. Positive correlations between exopolysaccharide production and proteolytic activity in skim milk were found some strains of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus. These results indicated that the high exocellular protease‐producing strains can produce high EPS in skim milk. The monomer compositions of the EPSs formed by selected five strains were analysed. Mannose dominated (99–100%) on the EPS produced by L. delbrueckii subsp. bulgaricus and S. thermophilusstrains (except L. delbrueckii subsp. bulgaricus 22) in skim milk and MRS/M17 medium. Besides, the EPSs of strains in skim milk contained small amount of lactose.