Streptococcus Thermophilus Research Articles

A polysaccharide from yogurt fermented by Lactobacillus bulgaricus and Streptococcus thermophilus: Structural characteristics and its alleviative effect on DSS-induced colitis in mice

A polysaccharide from yogurt fermented by Lactobacillus bulgaricus and Streptococcus thermophilus: Structural characteristics and its alleviative effect on DSS-induced colitis in mice

An insight into the functional alterations in the gut microbiome of healthy adults in response to a multi-strain probiotic intake: a single arm open label trial.

Probiotic supplements, by definition, provide a benefit to the host, but few studies have investigated the effect of probiotic supplements in healthy adult populations. The present, single arm, open label clinical trial, evaluated compositional and functional changes in the fecal microbiome of healthy adults after supplementation with a 14-strain probiotic. We analysed the effect of a 14-strain probiotic blend (Bacillus subtilis NCIMB 30223, Bifidobacterium bifidum NCIMB 30179, B. breve NCIMB 30180, B. infantis NCIMB 30181, B. longum NCIMB 30182, Lactobacillus helveticus NCIMB 30184, L. delbrueckii subsp. bulgaricus NCIMB 30186, Lacticaseibacillus paracasei NCIMB 30185, Lactiplantibacillus plantarum NCIMB 30187, Lacticaseibacillus rhamnosus NCIMB 30188, L. helveticus NCIMB 30224, Lactobacillus salivarius NCIMB 30225, Lactococcus lactis subsp. lactis NCIMB 30222, and Streptococcus thermophilus NCIMB 30189), on the faecal microbiota of healthy young adults (n=41) in a single arm study. The adults consumed 4 capsules daily of the 14 strain blend(8 billion colony forming units/day) for 8 weeks. Compositional and functional changes in faecal microbiota before and after supplementation were assessed using shotgun metagenomic sequencing. Fasting breath analysis, faecal biochemistry and bowel habits were also assessed. In healthy adult participants, no significant changes to the overall alpha- or beta-diversity was observed after 8 weeks of multi-strain probiotic supplementation. However, in a simplified model that considered only time and individual differences, significant decreases (p < 0.05) in family Odoribacteraceae and Bacteroidaceae abundance and a significant increase (p < 0.05) in genus Megamonas abundance were observed. At a functional level, there were significant changes in functional gene abundance related to several functional pathways, including phenylalanine metabolism, O-antigen nucleotide sugar biosynthesis, bacterial chemotaxis, and flagellar assembly. No significant changes in stool form or frequency, fecal biochemistry, or methane and hydrogen breath tests were observed. In healthy young adults, overall alpha- and beta-diversity did not change in response to probiotic intake even though modest compositional changes at the family and genus level were observed. However, at functional level, results identified changes in gene abundance for several functional pathways.

Happi: a hierarchical approach to pangenomics inference

Recovering metagenome-assembled genomes (MAGs) from shotgun sequencing data is an increasingly common task in microbiome studies, as MAGs provide deeper insight into the functional potential of both culturable and non-culturable microorganisms. However, metagenome-assembled genomes vary in quality and may contain omissions and contamination. These errors present challenges for detecting genes and comparing gene enrichment across sample types. To address this, we propose happi, an approach to testing hypotheses about gene enrichment that accounts for genome quality. We illustrate the advantages of happi over existing approaches using published Saccharibacteria MAGs, Streptococcus thermophilus MAGs, and via simulation.

Biochemical, Microstructural, and Probiotic Bacterial Patterns of Innovative Fresh Cheese Fortified with Helianthus tuberosus Tubers

Recently, functional foods have become the aim of customers and food producers. Integrating vegetable ingredients in the food industry is a productive goal to reduce costs while maintaining quality. Dried Jerusalem artichoke tubers powder (DJATP) was used as a novel approach in cheese manufacturing. Innovatively, its holding capacity features and impact on probiotic development were evaluated. The SEM microstructure image and biochemical analysis of DJATP confirmed higher water holding (5.31 g/g), oil absorption (1.99 g/g), and swelling (1.79 g/g) capacities than casein. DJATP (3%) supported the probiotic bacterial growth (Streptococcus thermophilus, Bifidobacterium bifidum, and Lactobacillus acidophilus) and accelerated the fermentation of skimmed milk more than pure inulin. When fortified with DJATP (3% or 6%), the cheese yield increased (24.66% and 27.85%, respectively) compared with 17.55% for control after storage (14 days). Besides the high levels of amino acids, minerals, flavonoids, phenols, and antioxidants, the probiotic bacteria in the DJATP-fortified cheese were better active, with better sensory features, recording the highest judging score (87.67) against the control (79.00). To our knowledge, no preceding studies used DJATP in fresh cheese manufacturing followed the probiotic behavior in DJATP or compared the microstructure of DJATP and casein. Instead of inulin, our novel approach suggests using DJATP as a prebiotic and an enhancer for fresh cheese quality and yield, all while being cost-effective. Future studies are encouraged to explore the potential use of DJATP in other functional cheese products.

Development and properties of functional yoghurt enriched with postbiotic produced by yoghurt cultures using cheese whey and skim milk.

This study aimed to examine the effects of supplementation of postbiotics derived from Streptococcus thermophilus (ST) and Lactobacillus delbrueckii subsp. bulgaricus (LB) in cheese whey (CW) and skim milk (SM) on antioxidant activity, viability of yoghurt starters, and quality parameters of low-fat yoghurt during 22 days of storage. The LB-CW (L delbrueckii ssp. bulgaricus postbiotic-containing cheese whey) sample exhibited the highest antioxidant activity, with 18.71% inhibition (p > 0.05). This sample also showed the highest water holding capacity (77.93%; p < 0.05) and a trend toward receiving the most favorable sensory attributes (p > 0.05) compared to the other samples. The LB-CW and LB-SM yoghurt samples exhibited significantly higher body and texture scores compared to the ST-SM-fortified yoghurt (p < 0.05). However, there was no significant difference in the overall acceptability of the LB-SM and ST-SM yoghurt samples across both starters (p > 0.05). Such findings highlight the potential of postbiotics as functional ingredients to enhance the nutritional and sensory aspects of yoghurt, further contributing to its appeal as a health-promoting product.

Activation of Csm6 ribonuclease by cyclic nucleotide binding: in an emergency, twist to open.

Type III CRISPR systems synthesize cyclic oligoadenylate (cOA) second messengers as part of a multi-faceted immune response against invading mobile genetic elements (MGEs). cOA activates non-specific CRISPR ancillary defence nucleases to create a hostile environment for MGE replication. Csm6 ribonucleases bind cOA using a CARF (CRISPR-associated Rossmann Fold) domain, resulting in activation of a fused HEPN (Higher Eukaryotes and Prokaryotes Nucleotide binding) ribonuclease domain. Csm6 enzymes are widely used in a new generation of diagnostic assays for the detection of specific nucleic acid species. However, the activation mechanism is not fully understood. Here we characterised the cyclic hexa-adenylate (cA6) activated Csm6' ribonuclease from the industrially important bacterium Streptococcus thermophilus. Crystal structures of Csm6' in the inactive and cA6 bound active states illuminate the conformational changes which trigger mRNA destruction. Upon binding of cA6, there is a close to 60° rotation between the CARF and HEPN domains, which causes the 'jaws' of the HEPN domain to open and reposition active site residues. Key to this transition is the 6H domain, a right-handed solenoid domain connecting the CARF and HEPN domains, which transmits the conformational changes for activation.

Dairy phages escape CRISPR defence of Streptococcus thermophilus via the anti-CRISPR AcrIIA3

Bacterial community collapse due to phage infection is a major risk in cheese making processes. As virulent phages are ubiquitous and diverse in milk fermentation factories, the use of phage-resistant lactic acid bacteria (LAB) is essential to obtain high-quality fermented dairy products. The LAB species Streptococcus thermophilus contains two type II-A CRISPR-Cas systems (CRISPR1 and CRISPR3) that can effectively protect against phage infection. However, virulent streptococcal phages carrying anti-CRISPR proteins (ACR) that block the activity of CRISPR-Cas systems have emerged in yogurt and cheese environments. For example, phages carrying AcrIIA5 can impede both CRISPR1 and CRISPR3 systems, while AcrIIA6 stops only CRISPR1. Here, we explore the activity and diversity of a third streptococcal phage anti-CRISPR protein, namely AcrIIA3. We were able to demonstrate that AcrIIA3 is efficiently active against the CRISPR3-Cas system of S. thermophilus. We used AlphaFold2 to infer the structure of AcrIIA3 and we predicted that this new family of functional ACR in virulent streptococcal phages has a new α-helical fold, with no previously identified structural homologs. Because ACR proteins are being explored as modulators in genome editing applications, we also tested AcrIIA3 against SpCas9. We found that AcrIIA3 could block SpCas9 in bacteria but not in human cells. Understanding the diversity and functioning of anti-defence mechanisms will be of importance in the design of long-term stable starter cultures.

Biofilm formation by heat-resistant dairy bacteria: multispecies biofilm model under static and dynamic conditions.

In the food industry, especially dairy, biofilms can be formed by heat-resistant spoilage and pathogenic bacteria from the farm. Such biofilms may persist throughout the processing chain and contaminate milk and dairy products continuously, increasing equipment cleaning, maintenance costs, and product recalls. Most biofilms are multispecies, yet most studies focus on single-species models. A multispecies model of dairy biofilm was developed under static and dynamic conditions using heat-resistant Bacillus licheniformis, Pseudomonas aeruginosa, Clostridium tyrobutyricum, Enterococcus faecalis, Streptococcus thermophilus, and Rothia kristinae isolated from dairies. C. tyrobutiricum and R. kristinae were weak producers of biofilm, whereas the other four were moderate to strong producers. Based on cross-streaking on agar, P. aeruginosa was found to inhibit B. licheniformis and E. faecalis. In multispecies biofilm formed on stainless steel in a CDC reactor fed microfiltered milk, the strong biofilm producers were dominant while the weak producers were barely detectable. All biofilm matrices were dispersed easily by proteinase K treatment but were less sensitive to DNase or carbohydrases. Further studies are needed to deepen our understanding of multispecies biofilms and interactions within to develop improved preventive strategies to control the proliferation of spoilage and pathogenic bacteria in dairies and other food processing environments. IMPORTANCE A model of multispecies biofilm was created to study biofilm formation by heat-resistant bacteria in the dairy industry. The biofilm formation potential was evaluated under static conditions. A continuous flow version was then developed to study multispecies biofilm formed on stainless steel in microfiltered milk under dynamic conditions encountered in dairy processing equipment. The study of biofilm composition and bacterial interactions therein will lead to more effective means of suppressing bacterial growth on food processing equipment and contamination of products with spoilage and pathogenic bacteria, which represent considerable economic loss.

Diversity of the Microbiota of Traditional Izmir Tulum and Izmir Brined Tulum Cheeses and Selection of Potential Probiotics.

High-throughput DNA sequencing (HTS) was used to study the microbial diversity of commercial traditional Izmir Tulum (IT) and Izmir Brined Tulum (IBT) cheeses from Izmir, Türkiye. Simultaneously, cultivation-dependent methods were used to isolate, identify and characterize bacterial strains displaying probiotic potential. At the phylum level, Firmicutes dominated the microbiota of both cheese types comprising >98% of the population. Thirty genera were observed, with Streptococcus being the most abundant genus and with Streptococcus thermophilus and S. infantarius subsp. infantarius being the most abundant species. Genera, including Bifidobacterium and Chryseobacterium, not previously associated with IT and IBT, were detected. IT cheeses displayed higher operational taxonomic units (OTUs; Richness) and diversity index (Simpson) than IBT cheeses; however, the difference between the diversity of the microbiota of IT and IBT cheese samples was not significant. Three Lacticaseibacillus paracasei strains isolated from IBT cheeses exhibited probiotic characteristics, which included capacity to survive under in vitro simulated gastrointestinal conditions, resistance to bile salts and potential to adhere to HT-29 human intestinal cells. These findings demonstrate that Tulum cheeses harbor bacterial genera not previously reported in this cheese and that some strains display probiotic characteristics.

Differences in the Proteolytic System of Lactic Acid Bacteria Affect the Release of DPP-IV Inhibitory Peptides from Whey Proteins

This work analyzed the antidiabetic activity of peptides from whey proteins after hydrolysis by Lactobacillus rhamnosus GG and Streptococcus thermophilus SY-102, emphasizing the differences between the proteolytic systems of both bacteria. Peptide fractions from whey proteins may have biological functions, such as antidiabetic functions, which inhibit the DPP-IV enzyme, and lactic acid bacteria could release them. A whey solution of 10% was fermented with selected lactic acid bacteria in monoculture and coculture, analyzing kinetic parameters and the proteolytic profile, using the 2,4,6-trinitrobenzene sulfonic acid technique for free amino groups’ determination and Tris-tricine polyacrylamide gel electrophoresis. An in vitro inhibition assay of the DPP-IV enzyme was used. The kinetic parameters showed a faster duplication rate in the monoculture with L. rhamnosus GG than in the co-culture, which was related to lactic acid production. Co-culture does not have the highest production of free amino groups and peptides. Still, peptide fractions with lower molecular weight (&lt;2 kDa) were found and showed a high DPP-IV inhibitory capacity that was maintained from the middle of the fermentation to the end (55.4%). In comparison, the monoculture of L. rhamnosus GG increased from 0 to 63.3%. This demonstrates that the proteolytic capacity and the proteolytic system of each lactic acid bacteria determine the structure of the released peptides.

A Thorough Investigation of the Microbiological, Physicochemical, and Sensory Properties of Ewe's Yoghurt Fermented by a Selected Multi-Strain Starter Culture.

This work was carried out with the aim to investigate the microbiological, physicochemical, and sensory properties of an innovative yoghurt produced from ewe's milk. Experimental yoghurt productions were performed with a commercial freeze-dried starter preparation and a natural milk starter culture (NMSC) of Streptococcus thermophilus and Lactobacillus delbrueckii. The two yoghurts did not differ for colour parameters, showing an average value of lightness, redness, and yellowness of 94.99, -3.74, and 9.37, respectively. The yoghurt produced using the NMSC as a fermenting agent was characterised by a significantly lower fat percentage and a higher antioxidant potential than commercial starters. Microbiological analysis confirmed the safety of the final product and a level of living lactic acid bacteria of 108 CFU/g. Sensory analysis revealed some differences among yoghurts regarding unpleasant odour, homogeneity, and persistence in the mouth, but the yoghurt processed with NMSC was more appreciated. Thus, the production of ewe's yoghurt fermented by a selected multi-strain starter culture represents an interesting strategy to enlarge the functional ovine dairy product portfolio.

Probiotic Characteristics of Streptococcus thermophilus and Lactobacillus bulgaricus as Influenced by New Food Sources.

The current research aimed to evaluate the potential effects of Solanum mammosum, Dioon mejiae, and Amanita caesarea on Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus survival and performance after exposure to different harsh conditions such as bile, acid, gastric juice, and lysozyme to mimic the digestive system from mouth to the intestine. Probiotic protease activity was observed to evaluate the proteolytic system. Probiotics were cultured in a broth mixed with plant material, and after incubation, the results were compared to the control sample. Therefore, plant material's total phenolic compound, total carotenoid compound, antioxidant activity, sugar profile, and acid profile were obtained to discuss their impact on the survival of probiotics. The results indicate that Amanita caesarea negatively affected probiotic survival in the bile tolerance test and positively affected Lactobacillus bulgaricus in the protease activity test. Otherwise, the other plant material did not change the results significantly (p > 0.05) compared to the control in different tests. Consequently, Solanum mammosum and Dioon mejiae had no significant effects (p > 0.05) in increasing probiotic survival.

Multidimensional evaluation of techno-functional properties of yoghurt bacteria

Microbial diversity in traditional foods is decreasing due to widespread industrial production, using a limited number of strains, and industrial products as starter cultures in homemade production. Yoghurt is a fermented product, and this decrease is most common. This study investigated the microbiological and physicochemical properties of 82 traditional and 37 industrial yoghurt samples. Four hundred thirty-nine lactic acid bacteria isolated were molecularly identified. Of the isolates, 223 were Lactobacillus bulgaricus, and 216 were Streptococcus thermophilus. Characteristics of the isolates such as acidification, arginine hydrolysis and gas production from glucose, H2O2 production, growth at different temperatures, pH and NaCl concentrations, exopolysaccharide production, proteolytic and lipolytic activity, l (+) lactic acid production, cholesterol assimilation, haemolytic activity, DNase activity, antibiotic resistance, and virulence gene were investigated. As a result, 4 L. bulgaricus and 6 S. thermophilus isolates were the best starter cultures for yoghurt production.

Cashew By-Product as a Functional Substrate for the Development of Probiotic Fermented Milk.

Cashew (Anacardium occidentale) processing generates a by-product (CB) with potential for health benefits and that could be a favorable ingredient to be added to a probiotic food matrix. This study aimed to assess the functional attributes of CB in fermented milk with a probiotic and a starter culture using in vitro gastrointestinal conditions. Two formulations were tested, without CB (Control Formulation-CF) and with CB (Test Formulation-TF), and the two strains most adapted to CB, the probiotic Lacticaseibacillus paracasei subsp. paracasei F19® and the starter Streptococcus thermophilus ST-M6®, were chosen to be fermented in the CF and the TF. During a 28-day period of refrigeration (4 °C), both strains used in the CF and TF maintained a population above 8.0 log CFU/mL. Strains cultured in the TF had a significant increase in total phenolic compounds and greater antioxidant potential during their shelf life, along with improved survival of F19® after in vitro-simulated gastrointestinal conditions. Our study revealed the promising potential of CB in the probiotic beverage. The CB-containing formulation (TF) also exhibited higher phenolic content and antioxidant activity. Furthermore, it acted as a protector for bacteria during gastrointestinal simulation, highlighting its potential as a healthy and sustainable product.

Preparation of Dendrobium officinale flower oligosaccharides and the value-added effects on three types of probiotics

The present study prepared Dendrobium officinale flower oligosaccharides and investigated their added value in vitro. The crude oligosaccharides obtained by water extraction and alcohol precipitation were purified by ultrafiltration, and the value-added effects of different concentrations of D. officinale flower oligosaccharides on Saccharomycetes, Lactobacillus bulgaricus, and Streptococcus thermophilus were examined. The in vitro growth kinetic models for the three types of probiotics were established according to the logistic equation. Our results showed that a concentration of 8 g/L D. officinale flower oligosaccharides was most suitable for promoting the growth of the three types of probiotics, and the growth rates were significantly improved compared to the control group. Nonlinear fitting was performed for the in vitro growth kinetic models of the three bacteria according to the logistic equation, and the degrees of fit reached 0.9895, 0.9899, and 0.99, respectively, indicating a good fit. These kinetic models suitably depicted the in vitro growth processes of the three bacteria. D. officinale flower oligosaccharides promote the growth of Saccharomycetes, L. bulgaricus and S. thermophilus and improve the physiological activities of these microorganisms. This study provides a theoretical basis for the application of D. officinale flower oligosaccharides in the development of probiotic products.

Study of the impact of electro-activated whey on the growth of Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus and the antibacterial potency of their supernatant against Salmonella enterica

The growth of Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus in co-culture and single culture in electro-activated whey was studied and the antibacterial potency of the supernatant obtained from their growth in this medium against Salmonella enterica was evaluated. The results obtained showed that electro-activated whey is an adequate medium for the growth of these bacteria without any supplementation. The high lactulose content up to 35% of total sugars, which is a prebiotic, and reductive redox potential of the electro-activated whey could be attributed to its adequacy as a whole growth medium for these bacteria. The supernatants obtained from the growth of these bacteria in electro-activated whey exhibited an antibacterial effect against Sal. enterica with MIC values of 75 IU for the supernatant of the mixed culture and of 150 IU for the supernatant of each bacterium grown as a single culture.

Metagenomic Insights into the Microbiome and Resistance Genes of Traditional Fermented Foods in Arabia.

This study uncovered microbial communities and evaluated the microbiological safety of traditional fermented foods consumed in the Arab region. Samples of dairy and non-dairy fermented foods-mish, jibneh, zabadi, and pickles-were collected from local markets in Saudi Arabia. Using the MiSeq system, samples were sequenced using 16S amplicons and shotgun metagenomics. Alpha and beta diversity indicated inter- and intra-variation in the studied fermented foods' bacterial communities. In the case of mish, the replicates were clustered. Twenty-one genera were found to be significantly different (FDR < 0.05) in abundance in pairwise comparison of fermented foods. Five high-quality, metagenome-assembled genomes (MAGs) of Lactococcus lactis, Lactobacillus helveticus, Pseudoalteromonas nigrifaciens, Streptococcus thermophiles, and Lactobacillus acetotolerans were retrieved from the shotgun sequencing representing the dominant taxa in the studied fermented foods. Additionally, 33 genes that cause antimicrobial resistance (ARGs) against ten different antibiotic classes were detected. Metabolic pathways were abundant in the studied metagenomes, such as amino acid metabolism, carbohydrate metabolism, cofactors, and vitamin biosynthesis. Metagenomic evaluation of Arabian fermented foods, including the identification of probiotics, pathogenic bacteria, and ARGs, illustrates the importance of microbiological analysis in evaluating their health effects.

Metabolic network construction reveals probiotic-specific alterations in the metabolic activity of a synthetic small intestinal community.

The gut microbiota plays a crucial role in maintaining overall health and probiotics have emerged as a promising microbiota-targeted therapy for improving human health. However, the molecular mechanisms of probiotics action in general and the targeting of small intestinal microbiota by probiotics are not well understood. To address this, we constructed a synthetic community of three species, which resembles the upper small intestinal microbiota. Our results indicate that probiotic supplementation can directly affect the metabolism of the community, resulting in colonization resistance in a probiotic-specific manner. Supplementation with Streptococcus thermophilus led to increased lactate production and a decrease in pH, while Lactobacillus casei supplementation increased the resistance to perturbations and nutrient utilization without affecting lactate production or pH. Additionally, when combined with kynurenine, Lactobacillus casei enhanced the kynurenine pathway metabolism resulting in elevated kynurenic acid levels and possibly indirect colonization resistance. Overall, our study reveals how selecting probiotics with distinct functional capacities can unlock the full potential of microbiota-targeted therapies.IMPORTANCEThe development of probiotic therapies targeted at the small intestinal microbiota represents a significant advancement in the field of probiotic interventions. This region poses unique opportunities due to its low number of gut microbiota, along with the presence of heightened immune and metabolic host responses. However, progress in this area has been hindered by a lack of detailed understanding regarding the molecular mechanisms through which probiotics exert their effects in the small intestine. Our study, utilizing a synthetic community of three small intestinal bacterial strains and the addition of two different probiotic species, and kynurenine as a representative dietary or endogenously produced compound, highlights the importance of selecting probiotic species with diverse genetic capabilities that complement the functional capacity of the resident microbiota, or alternatively, constructing a multispecies formula. This approach holds great promise for the development of effective probiotic therapies and underscores the need to consider the functional capacity of probiotic species when designing interventions.

Production and evaluation of a mutant galactose-utilizing strain of Streptococcus thermophilus for application in milk fermentation

Streptococcus thermophilus is a thermophilic gram-positive bacterium used in the production of fermented milk. Most S. thermophilus strains originating from milk can only use the glucose moiety of lactose as a carbon source, while the galactose moiety is secreted into the fermenting milk. In this study, one galactose-positive mutant (S. thermophilus IMAU80285Y) was produced by treating S. thermophilus IMAU80285 with the chemical mutagen, N-methyl-N′-nitro-N-nitrosoguanidine (NTG), and fermentation characteristics were evaluated. β-Galactosidase activity was higher in the mutant strain while glucokinase and pyruvate kinase activities were significantly decreased compared with the wild type. Sequencing revealed that S. thermophilus IMAU80285Y had mutations in the β-galactosidase, glucokinase and pyruvate genes. High performance liquid chromatography (HPLC) analysis demonstrated that accumulation of galactose in milk fermented by the mutant S. thermophilus IMAU80285Y was reduced by 55.4%, compared with the wild strain. Our results indicate that mutation enabled rerouting of the galactose metabolism pathways and provides new insights into using chemical mutagenesis to select strains with excellent characteristics for dairy application.

Preparation of sweet milk and yogurt containing d-tagatose by the l-arabinose isomerase derived from Lactobacillus rhamnosus

d-Tagatose is a novel low-calorie sweetener, but its application in milk and yogurt has not been explored. A novel l-arabinose isomerase gene was identified in Lactobacillus rhamnosus. The purified l-arabinose isomerase showed good thermal stability from 50 °C to 65 °C, and pH stability from 6.0 to 8.0. To prepare sweet milk, 3.77 × 10−7 kat/mL β-galactosidase and 9.02 × 10−8 kat/mL l-arabinose isomerase were added. After reaction at 65 °C for 3.5 h, the contents of glucose, d-galactose, and d-tagatose in milk were 25.00 g/L, 13.76 g/L, and 11.24 g/L, respectively, and lactose was not detected. Furthermore, Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus, with the respective characteristic of d-galactose, and glucose utilization were used as starters for sweet yogurt preparation. After fermentation, the yogurt contained 13.88 g/L of glucose, 10.13 g/L of d-galactose, and 10.90 g/L of d-tagatose, respectively. These results indicated the L. rhamnosusl-arabinose isomerase had a great potential for industrial application in sweetened milk and yogurt preparation.