Acidification Activity Research Articles

Legally admissible amounts of antibiotics in milk affect the growth of lactic acid bacteria

The antibiotic administration in dairy livestock is a current widespread practice. The purpose of the study was to evaluate whether milk from antibiotic‐treated animals, following the application of the withdrawal time and fully complying with European requirements in relation to residue content, affected the development of lactic acid bacteria. Forty‐five raw milk samples were collected after the withdrawal period and analysed to verify their compliance with the European maximum limits using four commercial screening tests. Lactobacillus delbrueckii subsp. bulgaricus growth and acidifying activity were delayed from 5 to 8 h in milk from cow treated with β‐lactams and sulfonamides present in low concentration (cephalosporins < 15 μg/kg; penicillins < 8 μg/kg; sulfonamides < 10 μg/kg) and their effect persisted over time. No influences were detected in Streptococcus thermophilus and Lb. helveticus development. The use of antibiotics can hamper the starter performances, opening questions about the safety of dairy products and human health.

A high-throughput spectroscopic method for pH determination in lactic acid bacteria screening

In this study, a colorimetric method was developed to enable the rapid determination of lactic acid bacteria (LAB) acidification ability by assessing the pH drop during juice fermentation. The proposed method used spectrophotometry to track pH variations induced by LAB, utilizing bromophenol blue as a pH indicator. This colorimetric method demonstrated linearity within the pH range of 2.50–5.70. Optimal performance was achieved with 5.0 % bromophenol blue, yielding a linear equation of y = 1.25x-0.78, with an R2 value of 0.99 upon regression analysis. The method's high accuracy, repeatability and reproducibility were validated through comparisons of pH values obtained using different matrices with those measured using glass electrodes/pH meters. Several Lactiplantibacillus plantarum strains with excellent acid-producing properties were identified through this method. Specifically, the growth of L20, L2 and L6 in MRS medium with a glucose concentration of 200 g/L for 24 h led to a pH decrease of 1.00 unit, while the growth of L20 and L21 in MRS with an ethanol concentration of 12 % (v/v) for 24 h resulted in a similar pH decrease. Strains L12, L14, and L18 could lower the pH of banana and lychee juices by more than 0.30 units at both 25 and 36°C. These results highlight the effectiveness of the method for rapidly screening LAB acidifying activity.

PbbHLH155 enhances iron deficiency tolerance in pear by directly activating PbFRO2 and PbbHLH38

Iron (Fe) deficiency is a general stress for many horticulture crops, causing leaf chlorosis and stunted growth. The basic–helix–loop–helix (bHLH) transcription factor (TF) was reported to function in Fe absorption; however, the regulatory mechanism of bHLH genes on iron absorption remains largely unclear in pear. In this study, we found that PbbHLH155 was significantly induced by Fe deficiency. Overexpression of PbbHLH155 in Arabidopsis thaliana and pear calli significantly increases resistance to Fe deficiency. The PbbHLH155-overexpressed Arabidopsis lines exhibited greener leaf color, higher Fe content, stronger Fe chelate reductase (FCR) and root acidification activity. The PbbHLH155 knockout pear calli showed lower Fe content and weaker FCR activity. Interestingly, PbbHLH155 inhibited the expressions of PbFRO2 and PbbHLH38, which were positive regulators in Fe-deficiency responses (FDR). Furthermore, yeast one-hybrid (Y1H) and Dual-Luciferase Reporter (DLR) assays revealed that PbbHLH155 directly binds to the promoters of PbFRO2 and PbbHLH38, thus activating their expression. Overall, our results showed that PbbHLH155 directly promote the expression of PbFRO2 and PbbHLH38 to activate FCR activity for iron absorption. This study provided valuable information for pear breeding.

Mechanistic study of the differences in lactic acid bacteria resistance to freeze- or spray-drying and storage

Lactobacillus delbrueckii subsp. bulgaricus and Lactiplantibacillus plantarum are two lactic acid bacteria (LAB) widely used in the food industry. The objective of this work was to assess the resistance of these bacteria to freeze- and spray-drying and study the mechanisms involved in their loss of activity. The culturability and acidifying activity were measured to determine the specific acidifying activity, while membrane integrity was studied by flow cytometry. The glass transitions temperature and the water activity of the dried bacterial suspensions were also determined. Fourier transform infrared (FTIR) micro-spectroscopy was used to study the biochemical composition of cells in an aqueous environment. All experiments were performed after freezing, drying and storage at 4, 23 and 37 °C. The results showed that Lb. bulgaricus CFL1 was sensitive to osmotic, mechanical, and thermal stresses, while Lpb. plantarum WCFS1 tolerated better the first two types of stress but was more sensitive to thermal stress. Moreover, FTIR results suggested that the sensitivity of Lb. bulgaricus CFL1 to freeze-drying could be attributed to membrane and cell wall degradation, whereas changes in nucleic acids and proteins would be responsible of heat inactivation of both strains associated with spray-drying. According to the activation energy values (47–85 kJ/mol), the functionality loss during storage is a chemically limited reaction. Still, the physical properties of the glassy matrix played a fundamental role in the rates of loss of activity and showed that a glass transition temperature 40 °C above the storage temperature is needed to reach good preservation during storage.Key points• Specific FTIR bands are proposed as markers of osmotic, mechanic and thermal stress• Lb. bulgaricus CFL1 was sensitive to all three stresses, Lpb. plantarum WCFS1 to thermal stress only• Activation energy revealed chemically limited reactions ruled the activity loss in storageGraphical abstract

Reduced synthesis of phospho-polysaccharide in Lactococcus as a strategy to evade phage infection

Lactococcus spp. are applied routinely in dairy fermentations and their consistent growth and associated acidification activity is critical to ensure the quality and safety of fermented dairy foods. Bacteriophages pose a significant threat to such fermentations and thus it is imperative to study how these bacteria may evade their viral predators in the relevant confined settings. Many lactococcal phages are known to specifically recognise and bind to cell wall polysaccharides (CWPSs) and particularly the phospho-polysaccharide (PSP) side chain component that is exposed on the host cell surface. In the present study, we generated derivatives of a lactococcal strain with reduced phage sensitivity to establish the mode of phage evasion. The resulting mutants were characterized using a combination of comparative genome analysis, microbiological and chemical analyses. Using these approaches, it was established that the phage-resistant derivatives incorporated mutations in genes within the cluster associated with CWPS biosynthesis resulting in growth and morphological defects that could revert when the selective pressure of phages was removed. Furthermore, the cell wall extracts of selected mutants revealed that the phage-resistant strains produced intact PSP but in significantly reduced amounts. The reduced availability of the PSP and the ability of lactococcal strains to revert rapidly to wild type growth and activity in the absence of phage pressure provides Lactococcus with the means to survive and evade phage attack.

Fermentation characteristics and postacidification of yogurt by Streptococcus thermophilus CICC 6038 and Lactobacillus delbrueckii ssp. bulgaricus CICC 6047 at optimal inoculum ratio

This study aimed to investigate the symbiosis between Streptococcus thermophilus CICC 6038 and Lactobacillus delbrueckii ssp. bulgaricus CICC 6047. In addition, the effect of their different inoculum ratios was determined, and comparison experiments of fermentation characteristics and storage stability of milk fermented by their monocultures and cocultures at optimal inoculum ratio were performed. We found the time to obtain pH 4.6 and ΔpH during storage varied among 6 inoculum ratios (1:1, 2:1, 10:1, 19:1, 50:1, 100:1). By the statistical model to evaluate the optimal ratio, the ratio of 19:1 was selected, which exhibited high acidification rate and low postacidification with pH values remaining between 4.2 and 4.4 after a 50-d storage. Among the 3 groups included in our analyses (i.e., the monocultures of S. thermophilus CICC 6038 [St] and Lb. bulgaricus CICC 6047 [Lb] and their cocultures [St+Lb] at 19:1), the coculture group showed higher acidification activity, improved rheological properties, richer typical volatile compounds, more desirable sensor quality after the fermentation process than the other 2 groups. However, the continuous accumulation of acetic acid during storage showed that acetic acid was more highly correlated with postacidification than d-lactic acid for the Lb group and St+Lb group. Our study emphasized the importance of selecting an appropriate bacterial consortium at the optimal inoculum ratio to achieve favorable fermentation performance and enhanced postacidification stability during storage.

Insight into the role of lactic acid bacteria in the development of a novel fermented pistachio (Pistacia vera L.) beverage

This study aimed to assess the fermentability of a pistachio-based beverage. The effects of lactic acid fermentation on the odor profile and the stability of the beverage were also assessed. To this end, a procedure for obtaining a pistachio beverage was developed, and the nutritional composition of the beverage was obtained. The beverage was characterized by a high content of fiber (2.9%), fat (4.6%), and protein (2%), and contained high amounts of K and Mg. For the experiment, 43 cultures of the following lactic acid bacteria were used: Companilactibacillus paralimentarius, Companilactibacillus kimchi, Levilactibacillus brevis, Lactiplantibacillu pentosus, Lactiplantibacillus plantarum, Lactiplantibacillus paraplantarum, Latilactobacillus curvatus, Leuconostoc pseudomesenteroides, and Furfurilactobacillus rossiae. The cultures were evaluated for the following technological characteristics: i) growth and acidifying activity, ii) production of exopolysaccharides; iii) presence of histidine decarboxylase (hdcA) gene; iv) antimicrobial activity against Listeria innocua. The cultures were used in model pistachio-based fermentations to assess their ability to grow and acidify. The odor profile of the beverage after 24 h fermentation was assessed using an electronic nose system (E-nose). The pistachio-based beverage resulted an optimal substrate for lactic acid bacteria that reached loads between 8 and 10 log CFU/mL and acidified the beverage to pH values between 4 and 5.5. In the beverage, viable counts of all cultures remained above 8 log CFU/mL after 30 days of storage at 4 °C. The E-nose analysis represented a valid screening method to evaluate the effects of the fermentative activity of microbial starters on the qualitative characteristics of this novel food matrix.

Evidence That PbrSAUR72 Contributes to Iron Deficiency Tolerance in Pears by Facilitating Iron Absorption.

Iron is an essential trace element for plants; however, low bioactive Fe in soil continuously places plants in an Fe-deficient environment, triggering oxidative damage. To cope with this, plants make a series of alterations to increase Fe acquisition; however, this regulatory network needs further investigation. In this study, we found notably decreased indoleacetic acid (IAA) content in chlorotic pear (Pyrus bretschneideri Rehd.) leaves caused by Fe deficiency. Furthermore, IAA treatment slightly induced regreening by increasing chlorophyll synthesis and Fe2+ accumulation. At that point, we identified PbrSAUR72 as a key negative effector output of auxin signaling and established its close relationship to Fe deficiency. Furthermore, the transient PbrSAUR72 overexpression could form regreening spots with increased IAA and Fe2+ content in chlorotic pear leaves, whereas its transient silencing does the opposite in normal pear leaves. In addition, cytoplasm-localized PbrSAUR72 exhibits root expression preferences and displays high homology to AtSAUR40/72. This promotes salt tolerance in plants, indicating a putative role for PbrSAUR72 in abiotic stress responses. Indeed, transgenic plants of Solanum lycopersicum and Arabidopsis thaliana overexpressing PbrSAUR72 displayed less sensitivity to Fe deficiency, accompanied by substantially elevated expression of Fe-induced genes, such as FER/FIT, HA, and bHLH39/100. These result in higher ferric chelate reductase and root pH acidification activities, thereby hastening Fe absorption in transgenic plants under an Fe-deficient condition. Moreover, the ectopic overexpression of PbrSAUR72 inhibited reactive oxygen species production in response to Fe deficiency. These findings contribute to a new understanding of PbrSAURs and its involvement in Fe deficiency, providing new insights for the further study of the regulatory mechanisms underlying the Fe deficiency response.

Fermented Milk Produced with Goat Milk Enriched with PUFA Omega-3 by Supplementation of Diet with Extruded Linseed

This research aimed to evaluate goat milk rich in Omega-3 PUFA from animals fed extruded flaxseed as a raw material to produce fermented milk using beneficial lactobacilli. Experimental fermented milks were produced using Lacticaseibacillus paracasei Shirota and two potential probiotic lactobacilli, namely Lacticaseibacillus rhamnosus A2 and Lacticaseibacillus paracasei FS109. The fermented milks were produced using milk from goats fed a basal diet without any supplementation (CON) and milk from goats supplemented with 200 g/d of extruded linseed (LIN). All lactobacilli tested grew well both in CON and LIN milk, reaching high numbers during fermentation. The colony count ranged between 8 and 10 Log CFU/mL, despite slow acidification activity, which occurred especially in milk fermented by L. FS109. By contrast, an undesired post-acidification occurred, more pronounced in CON than in LIN milk, which still highlighted the strong acid-tolerance of L. Shirota and L. rhamnosus A2 in particular. This research showed that goat milk enriched in PUFA had no negative effect on the viability of the tested Lactobacilli. Both values of L. Shirota and L. rhamnosus “live cells” throughout the cold storage of the products were higher than those recommended to guarantee the quality of fermented milk products, making them beneficial to consumers’ health.

Assessment of technological and functional features of Lactiplantibacillus and Fructobacillus strains isolated from Opuntia ficus-indica fruits

Opuntia ficus-indica fruits are outstanding for their sensory attributes and multiple health benefits. However, this fruit is highly perishable, and substantial efforts have been carried out to extend its shelf-life. Lactic fermentation of fruits by-products using autochthonous bacteria arises as relevant technology for preserving vegetables and their by-products. In this study, autochthonous Lactiplantibacillus plantarum and Fructobacillus fructosus strains previously selected from Opuntia ficus-indica fruits of Northwestern Argentina were characterized according to their technological and functional properties to select the most suitable for the production of fermented cactus pear products. L. plantarum strains showed better acidifying activity, decreasing the pH of the juice by about 2.9 units in 24 h. All the strains studied produced lactic and propionic acids, and L.plantarum S-811 and S-TF2 strains and F. fructosus S-TF7 strain were the better lactic acid producers, with values around 9.5 g/l. These strains also displayed antimicrobial activities against undesirable pathogen bacteria, showed a safety profile typical of lactic acid bacteria, and the juice fermented with these strains preserves the phenolic compounds content and antioxidant activity of unfermented juice. The obtained results showed the potential of L.plantarum S-811 and S-TF2, and F. fructosus S-22 for their use as starters for the fermentation of cactus pear by-products, standing out L.plantarum S-811 for its potentiality to elaborate a fermented cactus pear beverage. The cactus pear juice fermented by L.plantarum S-811 showed physicochemical and microbiological stability that favors juice shelf-life. Besides, fermentation conferred distinctive sensory features to the cactus pear juice without influencing consumers' overall acceptability.

Rhizosphere Acidification Determines Phosphorus Availability in Calcareous Soil and Influences Faba Bean (Vicia faba) Tolerance to P Deficiency

Calcareous soils are known for their alkaline pH-promoting insoluble forms of certain nutrients, including phosphorus (P). Rhizosphere acidification is one of the main physiological mechanisms of phosphorus mobilization by plants. However, specific and genotypic differences in response to P deficiency are often observed, giving some genotypes particular tolerance abilities. This genetic potential gives us a new opportunity to colonize unused lands, improve yield in problematic soils, and install sustainable agrosystems. To this end, a potted experiment was conducted on three faba bean genotypes (Seville, SEV; Aguadulce, AGUA; and Tunisian, TUN) cultivated on calcareous soil (CS), as compared to fertile soil (FS). Measurements are made on plant growth, the SPAD index, photosynthesis, P distribution, rhizosphere acidification, and related interrelationships. Calcareous soil induced specific symptoms of P deficiency, reduced P concentration and decreased SPAD index, net photosynthesis, and plant growth. Rhizosphere acidification was significantly stimulated in CS. This activity determines the genotypic differences in response to P deficiency in faba bean. The genotype TUN was more adapted to calcareous-induced P deficiency than AGUA and SEV by increasing acidification activity, decreasing pH by 0.6 units in the rhizosphere, and having higher biomass production, photosynthesis, P remobilization, and P accumulation. The key functional traits (plant growth, chlorophyll biosynthesis, and photosynthesis) are strictly dependent on P availability, which remains in close relationship with the acidification capacity (AC). The tolerant genotype (TUN) expressed a lower stress index (SI) but higher P use efficiency (PUE), H-ATPase activity, and P uptake and translocation to shoots (PT), allowing it to maintain better metabolic functioning. AC, PT, PUE, and SI are among the main traits of P management in calcareous soils that promote resilient crops.

Multiobjective optimization of frozen and freeze-dried Lactobacillus delbrueckii subsp. bulgaricus CFL1 production via the modification of fermentation conditions.

This study investigates the individual and combined effects of fermentation parameters for improving cell biomass productivity and the resistance to freezing, freeze-drying, and freeze-dried storage of Lactobacillus delbrueckii subsp. bulgaricus CFL1. Cells were cultivated at different temperatures (42°C and 37°C) and pH values (5.8 and 4.8) and harvested at various growth phases (mid-exponential, deceleration, and stationary growth phases). Specific acidifying activity was determined after fermentation, freezing, freeze-drying, and freeze-dried storage. Multiple regression analyses were performed to identify the effects of fermentation parameters on the specific acidifying activity losses and to generate the corresponding 3D response surfaces. A multiobjective decision approach was applied to optimize biomass productivity and specific acidifying activity. The temperature positively influenced biomass productivity, whereas low pH during growth reduced the loss of specific acidifying activity after freezing and freeze-drying. Furthermore, freeze-drying resistance was favored by increased harvest time. Productivity, and freezing and freeze-drying resistances of L. delbrueckii subsp. bulgaricus CFL1 were differentially affected by the fermentation parameters studied. There was no single fermentation condition that improved both productivity and resistance to freezing and freeze-drying. Thus, Pareto fronts were helpful to optimize productivity and resistance, when cells were grown at 42°C, pH 4.8, and harvested at the deceleration phase.

Isolation and Screening of Lactic Acid Bacteria From Sumbawa Buffalo Milk (Bubalus bubalis) as Potential Starter Cultures

The Sumbawa buffalo (Bubalus bubalis) is one of the ruminant livestock in Indonesia that not only contributes to fulfilling meat requirements but also milk. Besides containing nutrients that are very beneficial for human health, buffalo milk is also a potential source of lactic acid bacteria (LAB) with technological and functional properties. Lactic acid bacteria have been utilized as starter cultures in various fermented products. This study aimed to isolate LAB from Sumbawa buffalo milk and to identify the potential isolate as a starter culture. The screening of LAB as a starter culture was based on some technological properties, including proteolytic activity, lipolytic activity, exopolysaccharide (EPS) production, antibacterial activity, antibiotic sensitivity, hemolytic activity, and acidification activity Data were analyzed statistically using one-way ANOVA and Tukey’s post hoc test at a 5% significance level. A total of 21 isolates were isolated from fresh buffalo milk, with a LAB total was 4.7x105 CFU.mL-1. All the isolates were characterized as Gram-positive with cocci-shaped. The SA8 isolate was selected as the most potential candidate as a starter culture because it has fulfilled the criteria such as the highest proteolytic activity, the lowest lipolytic activity, producing EPS, potential antagonistic activity against Bacillus cereus, Escherichia coli, and Salmonella Typhi, and sensitivity to cefazolin, intermediate to erythromycin and cinoxacin, non-pathogen, as well as the most rapid acidification activity. The SA8 isolate was identified as Enterococcus lactis with a similarity level of 99.99% towards strain BT159. This indigenous LAB was a potential starter culture of Sumbawa fermented buffalo milk to increase the diversification of products derived from buffalo milk.

The Role of Exopolysaccharide-Producing Streptococcus thermophilus on Physical Properties of Stirred Skim Milk Gel

The techno-functionality of exopolysaccharides (EPS) from Streptococcus thermophilus in stirred fermented milk is affected by several extrinsic (e.g., base milk composition) and intrinsic (e.g., amount and properties of EPS) factors. The aim of this study was to use skim milk models to identify the key factors that influence the physical properties of stirred fermented milk with EPS. For that, fermentation was carried out with one of three single S. thermophilus strains (intrinsic factors) at two casein:whey protein ratios of the base milk, two acidification activities of the starters, and two fermentation temperatures (extrinsic factors). The effects of the factors on the acidification kinetics, EPS amount, susceptibility to syneresis, and texture properties were then discriminated by a multivariate ANOVA-simultaneous component analysis. Strains producing ropy EPS mainly determined the texture properties, whereas the extrinsic factors primarily affected the acidification kinetics and EPS amount. When capsular EPS were also present, the syneresis was lower; however, this effect was more pronounced after enrichment of base milk with whey protein. The EPS amount did not correlate with the texture or syneresis, pointing to the importance of other factors such as the EPS location (type) and EPS–protein interactions for their functionality in stirred fermented milk.

Effects of different enzyme extraction methods on the properties and prebiotic activity of soybean hull polysaccharides

In this study, five different processes, including hot water (HW-ASP), single enzyme (cellulase, pectinase and papain; C-ASP, PE-ASP, and P-ASP), and compound-enzyme (cellulose: pectinase: papain = 3:3:1; CE-ASP) for the extraction of soybean hull polysaccharides (ASPs) were employed, and the characterization and prebiotics activity of five polysaccharides were analyzed. These polysaccharides possessed different primary structural characteristics, including molecular weight distribution, monosaccharide composition, chemical composition, surface morphology, potential particle size, etc., while similar functional groups. In vitro digestibility assay indicated that C-ASP had strong resistance to gastric juice hydrolysis and α-amylase as compared with HW-ASP. Furthermore, C-ASP elevated the acidifying activity and promoted the growth of probiotics (Lactobacillus paracasei, Lactobacillus rhamnosus, and Lactobacillus acidophilus) during the fermentation (p < 0.05). C-ASP improved the levels of total short-chain fatty acids (SCFAs) and had better prebiotic activity than HW-ASP (p < 0.05). These findings denote that enzyme-assisted polysaccharides extracted from soybean hulls have the potential to be served as novel probiotics.

Characterization of lactic acid bacteria isolated from budu, a West Sumatra fish fermentation product, and their ability to produce exopolysaccharides

Background: Probiotics are instrumental in maintaining the equilibrium of the gut microbiota and improving the health of the human body. This study examined the presence and physiological features, including the ability to produce exopolysaccharides, of lactic acid bacteria from fermented Tenggiri (Scomberomorus guttatus) and Talang (Chorinemus spp.) fish, also known as budu fish. Methods: Lactic acid bacteria were isolated from budu fish. These bacteria were characterized to determine tolerance to gastric pH values, growth curve, inhibitory ability against pathogenic bacteria, and ability to produce exopolysaccharides and to perform a molecular identification. Results: Twenty-nine lactic acid bacteria isolates from budu fish were determined to be of the Pediococcus species. Assessment of the physiological characteristics showed that Pediococcus sp. had a high acidifying activity and could grow at a pH between 2 and 11; the pH of the supernatant after 36 hours of incubation was 4.49. In terms of inhibitory activity against pathogenic bacteria, Pediococcus sp. demonstrated an inhibitory diameter of 20.5 mm against Escherichia coli, 23.0 mm against Staphylococcus aureus, and 21.0 mm against Salmonella thypi. The Pediococcus sp. strain produced exopolysaccharides ranging from 870 to 1910 mg/l and had 100% similarity with Pediococcus pentosaceus strain 4942. Conclusions: This study confirmed the presence of Pediococcus pentosaceus strain 4942 in budu fish, which can be used as a new probiotic based on its capabilities to kill pathogenic bacteria and produce exopolysaccharide compounds.

Radiodynamic Therapy with Acridine Orange Is an Effective Treatment for Bone Metastases.

Current multimodal treatment of bone metastases is partially effective and often associated with side effects, and novel therapeutic options are needed. Acridine orange is a photosensitizing molecule that accumulates in acidic compartments. After photo- or radiodynamic activation (AO-PDT or AO-RDT), acridine orange can induce lysosomal-mediated cell death, and we explored AO-RDT as an acid-targeted anticancer therapy for bone metastases. We used osteotropic carcinoma cells and human osteoclasts to assess the extracellular acidification and invasiveness of cancer cells, acridine orange uptake and lysosomal pH/stability, and the AO-RDT cytotoxicity in vitro. We then used a xenograft model of bone metastasis to compare AO-RDT to another antiacid therapeutic strategy (omeprazole). Carcinoma cells showed extracellular acidification activity and tumor-derived acidosis enhanced cancer invasiveness. Furthermore, cancer cells accumulated acridine orange more than osteoclasts and were more sensitive to lysosomal death. In vivo, omeprazole did not reduce osteolysis, whereas AO-RDT promoted cancer cell necrosis and inhibited tumor-induced bone resorption, without affecting osteoclasts. In conclusion, AO-RDT was selectively toxic only for carcinoma cells and effective to impair both tumor expansion in bone and tumor-associated osteolysis. We therefore suggest the use of AO-RDT, in combination with the standard antiresorptive therapies, to reduce disease burden in bone metastasis.

Development of fermented milk using food-grade recombinant Lactococcus lactis NZ3900

Fermented milk has been associated with the improvement of human health for decades. Food-grade Lactococcus lactis NZ3900 is a potential host for producing and delivering various biologics, including oral vaccines, hence it could enhance the functionality of fermented milk as a starter culture. A cultured fermented milk product was developed in this study using the food-grade recombinant L. lactis NZ3900 harboring plasmid pNZ8149. Response surface methodology was used to optimize the inoculum concentration (5–15% v/v), fermentation temperature (23–37 °C), and fermentation time (18–30 h) to enhance the viability, acidification activity, viscosity, and minimize syneresis of the L. lactis NZ3900-fermented milk using response surface methodology. The optimal inoculum concentration and fermentation conditions for L. lactis NZ3900-fermented milk are 12.5% (v/v) inoculum, 28 °C fermentation temperature, and 30 h of fermentation time, resulting in higher viability (9.64 log10 CFU/mL), acidification activity (pH 4.42, 0.78% titratable acidity), viscosity (11,096.9 mPa·s), and comparable syneresis (63.62%) against commercial fermented milk products. This shows that food-grade L. lactis NZ3900 can be used as a starter culture, and NZ3900-fermented milk could be used as a functional drink for oral vaccine delivery.

Characterization of starter cultures and nutritional properties of Pediococcus acidilactici NCDC 252: A potential probiotic of dairy origin

NCDC 252, a potential probiotic, was studied for starter properties. It exhibited proteolytic activity in cow, buffalo, and goat milk and acidified skim milk and cheese by lowering their pH. It survived heat treatment and also in the presence of salt and ethanol. This suggests its fermentation ability for dairy products and beverages. The presence of genes for heavy metal tolerance and vitamins' biosynthesis in its genome suggests its ability for heavy metal detoxification and de novo vitamin synthesis, respectively. HPLC studies confirmed vitamin B12 production. These studies suggest NCDC 252 to be a potential starter culture that can be used for food fortification. Practical applications NCDC 252 possessed α-glucosidase activity. α-glucosidase hydrolyses disaccharides to glucose. The utilization of otherwise indigestible oligosaccharides by humans is an important probiotic attribute. It also exhibited high proteolytic activity and rapid acidification activity. Probiotic strain with proteolytic activity is a new strategy for the production of novel functional foods rich in bioactive peptides. NCDC 252 exhibited high acidification that might contribute to the organoleptic and functional properties of fermented food products. Thus, it should be selected as a part of the starter culture in dairy industries. Production of vitamin B12 is considered an important probiotic characteristic of NCDC 252 for in situ vitamin B12 fortification in the food industry. Production and delivering health-promoting compounds by LAB is a very promising field. The ability of LAB to enrich the food and human body with the aid of producing vitamins and cofactors further enhance the scope of its utilization for medicinal and health applications.

Characterization, Acidifying, and Antibacterial Activity of Lactic Acid Bacteria Against Spoilage Strains Present in Chicken Meat

Nowadays, through their beneficial roles, lactic acid bacteria have been used as natural additives for the formulation of several products especially in the food industry; as they reduce the pathogen load and improve the quality of fermented food. This work focuses on the technological study of five homolactic strains isolated from three fermented barley preparations belonging to three species: Lactobacillus plantarum, Pediococcus spp, and Lactococcus lactis ssp. The experiment focused on testing their acidifying activity and their antibacterial action against a range of spoilage strains isolated from chicken meat. The identification was carried out based on the study of the cultural, morphological characters and biochemical tests which revealed the presence of five strains namely: Escherichia Coli, Salmonella sp, Staphylococcus aureus, Proteus vulgaris, and Klebsiella pneumonia. The results obtained showed that the strains (SC1, SC4, and SC5) have acidifying activities, in parallel with a significant antibacterial effect compared to the other strains (SC2, SC3) whose respective values were 1.63±0.07%, 0.99±0.23% and 1.29±0.65% for SC1, SC4 and SC5. Moreover, the cell-free culture supernatant (CFCS) inhibition zones range from 19.5 ± 0.70 mm to 10.25 ± 0.35 mm.