Impact Of Lactic Acid Bacteria Research Articles

Functional and biochemical characterization of pre-fermented ingredients obtained by the fermentation of durum wheat by-products

This work was aimed to characterize functional and biochemical parameters of a bakery ingredient prepared with durum wheat by-products (micronized bran and middling) fermented by a selected microbial consortium composed of yeasts and lactic acid bacteria. The unfermented milling by-products mixture and the mixture fermented by a baker’s yeast were used as reference. The innovative ingredient showed more stable colour indexes compared to the references, a more complex profile in volatile molecules characterized by a higher presence of alcohols, ketones and acids compared to the references. A significant increase in the content of peptides, short chain fatty acids, total phenols, antioxidant activity and prebiotic activity together with a reduction in phytic acid content was observed in the samples fermented by the selected microbial consortium compared to the references. This work provides information on the impact of lactic acid bacteria and yeasts on functional and biochemical characteristics of fermented milling by-products.

In-situ substitution and community dynamics modeling for enhanced safety in Chinese rice wine brewing

This research paper focuses on the application of the “Design-Build-Test-Learn” framework to design and evaluate a synthetic microbial community aimed at studying the impact of Lactic Acid Bacteria (LAB) interactions and fitness on the formation of biogenic amines (BAs) in Chinese rice wine (CRW). The study reveals a close correlation between the assembly model of LAB and the accumulation of BAs in CRW, and multiple interactions were observed between amine-producing and non-amine-producing LAB, including commensalism, amensalism, and competition. The commensalism among amine-producing LAB was found to promote BAs accumulation through metabolic cross-feeding of amino acids. Moreover, the higher-order interaction community was designed to regulate the BAs formation effectively. For instance, the interference of Lactiplantibacillus plantarum (ACBC271) resulted in the elimination of amine-producing LAB viability, resulting in a 22% decrease (not exceeding 43.54 mg/L) in the total amount of BAs. Simulation of community dynamics models further suggests that LAB with quantitative social interactions can effectively control LAB accumulation in CRW by forecasting fluctuation in BAs generation through fitness competition and metabolic interference. Overall, this study provides valuable insights into the complex interaction networks within microbial communities in traditional fermentation ecosystems. It also proposes a novel approach for quality control of nitrogen food safety factors in fermented foods.

Effect of lactic acid bacteria and Bacillus on anthracnose disease in postharvest papaya fruit

Abstract. Thi QVC, Dung TQ, Huynh NTN, Truc NT, Thuy NP. 2023. Effect of lactic acid bacteria and Bacillus on anthracnose disease in postharvest papaya fruit. Biodiversitas 24: 5883-5894. Anthracnose disease of papaya fruit caused by Colletotrichum (isolate TD1), identified by 5.8S rRNA sequence homology, is a main obstacle in papaya fruit, influencing fruit quality and minimizing shelf life. Therefore, to diminish the disease and sustain the fruit quality, the impact of Lactic Acid Bacteria (LAB) and Bacillus on the growth of anthracnose disease and fruit quality was investigated in vitro and in vivo. Furthermore, 13 LAB and 12 Bacillus isolates were collected from traditional fermented vegetables and papaya rhizospheric soils. The results showed that 13 LAB isolates and 6 isolates of Bacillus were inhibitory against Colletotrichum in an in vitro test. Two isolates of LDC11 and BHL21 with the highest antifungal activity were selected to evaluate their effect on Colletotrichum growth and papaya fruit quality under in vivo conditions. These findings indicated that the isolates LDC11 and BHL21 at a density of 106 CFU/mL reduced the disease incidence and severity. The LAB and Bacillus treated papaya fruit increased a number of parameters, such as weight loss, TSS, and L*, a*, and b* values. However, vitamin C content, TA, and fruit firmness were reduced compared to the control. The research shows a potential applications of LAB and Bacillus in the postharvest preservation of papaya fruit. To our knowledge, this is the first study to apply Bacillus and LAB bacteria to control diseases in postharvest papaya in Vietnam.

Effects of lactic acid bacteria-derived fermented feed on the taste and quality of duck meat

The present study aimed to examine the impact of lactic acid bacteria- fermented feed (FF) on the taste and quality of duck meat, in addition to elucidating the potential metabolomic mechanism at play. The findings revealed that ducks fed with FF exhibited elevated pH levels and reduced cooking loss in their meat when compared to the control group. In addition, the sensory evaluation and e-tongue analysis revealed that the tenderness, juiciness, umami, richness, saltiness, and sweetness of duck meat were all enhanced by feeding FF. Moreover, an examination of the metabolome using 1H nuclear magnetic resonance (1H NMR) identified the principal differential metabolites that exhibited a correlation with taste, which included 2-aminoadipate, glucose, glycine, N-acetylcysteine, niacinamide, proline, and threonine. Furthermore, the differential metabolites that exhibited the greatest enrichment in duck meat could be primarily traced to glutathione metabolism, glycine, serine and threonine metabolism, taurine and hypotaurine metabolism. The potential factors contributing to the effect of FF and basic commercial duck feed (CF) were found to be primarily regulated via the aforementioned metabolic pathways. The study, therefore, offers a viable approach for enhancing the taste and quality of duck meat.

Antiobesity and Antioxidative Effect of Fermented Brown Rice Using In Vitro with In Vivo Caenorhabditis elegans Model

Naturally occurring phytochemicals from plants or grains are crucial in reducing various metabolic disorders. Bioactive phytonutrients are abundant in the Asian dietary staple, brown rice. This research evaluated the impact of lactic acid bacteria (LABs) bioconversion and fermentation on antioxidant and antiobesity activities and ferulic acid content in brown rice. The combination of bioconversion with Pediococcus acidilactici MNL5 among all LABs used showed a synergistic impact with 24 h of solid-state brown rice fermentation. The 24-h MNL5 fermented brown rice (FBR) demonstrated the most potent pancreatic lipase inhibitory activity (85.5 ± 1.25%) compared to raw brown rice (RBR) (54.4 ± 0.86%). The antioxidant potential of MNL5-FBR was also found to be highest in the DPPH assay (124.40 ± 2.40 mg Trolox Equiv./100 g, DW), ABTS assay (130.52 ± 2.32 mg Trolox Equiv./100 g, DW), and FRAP assay (116.16 ± 2.42 mg Trolox Equiv./100 g, DW). Based on higher antioxidant and antiobesity activities, samples were quantified for ferulic acid content using the HPLC-MS/MS approach. Furthermore, C. elegans supplementation with FBR showed enhanced life span and lipid reduction in fluorescence microscope analysis compared to the control. Our results indicate that the expression study using the C. elegans model (N2 and Daf-2 models) fat gene was conducted, showing a lowering of obesity ability in FBR-fed worms. Our study indicates that FBR has improved antioxidant and antiobesity actions, especially in MNL5-FBR, and can be employed to develop functional foods that combat obesity.

Exploring the impact of lactic acid bacteria on the biocontrol of toxigenic Fusarium spp. and their main mycotoxins

The occurrence of fungi and mycotoxins in foods is a serious global problem. Most of the regulated mycotoxins in food are produced by Fusarium spp. This work aimed to assess the antifungal activity of selected lactic acid bacteria (LAB) strains against the main toxigenic Fusarium spp. isolated from cereals. Various machine learning (ML) algorithms such as neural networks (NN), random forest (RF), extreme gradient boosted trees (XGBoost), and multiple linear regression (MLR), were applied to develop models able to predict the percentage of fungal growth inhibition caused by the LAB strains tested. In addition, the ability of the assayed LAB strains to reduce/inhibit the production of the main mycotoxins associated with these fungi was studied by UPLC-MS/MS. All assays were performed at 20, 25, and 30 °C in dual culture (LAB plus fungus) on MRS agar-cereal-based media. All factors and their interactions very significantly influenced the percentage of growth inhibition compared to controls. The efficacy of LAB strains was higher at 20 °C followed by 30 °C and 25 °C. Overall, the order of susceptibility of the fungi to LAB was F. oxysporum > F. poae = F. culmorum ≥ F. sporotrichioides > F. langsethiae > F. graminearum > F. subglutinans > F. verticillioides. In general, the most effective LAB was Leuconostoc mesenteroides ssp. mesenteroides (T3Y6b), and the least effective were Latilactobacillus sakei ssp. carnosus (T3MM1 and T3Y2). XGBoost and RF were the algorithms that produced the most accurate predicting models of fungal growth inhibition. Mycotoxin levels were usually lower when fungal growth decreased. In the cultures of F. langsethiae treated with LAB, T-2 and HT-2 toxins were not detected except in the treatments with Pediococcus pentosaceus (M9MM5b, S11sMM1, and S1M4). These three strains of P. pentosaceus, L. mesenteroides ssp. mesenteroides (T3Y6b) and L. mesenteroides ssp. dextranicum (T2MM3) inhibited fumonisin production in cultures of F. proliferatum and F. verticillioides. In F. culmorum cultures, zearalenone production was inhibited by all LAB strains, except L. sakei ssp. carnosus (T3MM1) and Companilactobacillus farciminis (T3Y6c), whereas deoxynivalenol and 3-acetyldeoxynivalenol were only detected in cultures of L. sakei ssp. carnosus (T3MM1). The results show that an appropriate selection and use of LAB strains can be one of the most impacting tools in the control of toxigenic Fusarium spp. and their mycotoxins in food and therefore one of the most promising strategies in terms of efficiency, positive impact on the environment, food safety, food security, and international economy.

Research Update on the Impact of Lactic Acid Bacteria on the Substance Metabolism, Flavor, and Quality Characteristics of Fermented Meat Products.

This paper reviews the effects of domestic and foreign influences on the substance metabolism pathways and the flavor and flora of LAB in fermented meat products to provide a new theoretical basis for developing new products for the industrial application of lactic acid bacteria (LAB) in fermented meat products. LAB are extensively used among commonly fermented ingredients, such as fermented meat products and yogurt. As fermenting agents, LAB metabolize proteins, lipids, and glycogen in meat products through their enzyme system, which affects the tricarboxylic acid cycle, fatty acid metabolism, amino acid decomposition, and other metabolic processes, and decompose biological macromolecules into small molecules, adding a special flavor with a certain functionality to the final product. Metabolites of LAB in the fermentation process also exert nitrite degradation, as well as antibacterial and antioxidant functions, which improve the physical and chemical qualities of fermented meat products. While fermenting meat products, LAB not only add unique flavor substances to the products, but also improve the safety profile of fermented foods.

Mixed dairy and plant-based yogurt alternatives: Improving their physical and sensorial properties through formulation and lactic acid bacteria cocultures

Food transition requires incorporating more plant-based ingredients in our diet, thus leading to the development of new plant-based products, such as yogurt alternatives (YAs). This study aimed at evaluating the impact of lactic acid bacteria (LAB) cocultures and formulation on the physico-chemical and sensory properties of YAs. YAs were made by emulsifying anhydrous milk fat (AMF) or coconut oil in milk and lupin protein suspensions. The starters used, in mono- and cocultures, were the strains Lactococcus lactis NCDO2125, Enteroccocus faecalis CIRM-BIA2412 and Lactiplantibacillus plantarum CIRM-BIA1524. Textural properties and metabolites of YAs were evaluated and their sensory properties compared using a sorting task. Some cocultures led to higher firmness, viscosity, and water holding capacity of YAs, compared to monocultures. AMF and a milk:lupin protein ratio of 67:33 gave firmer and more viscous YAs. YAs were sensorially discriminated on the basis of protein ratio and fat type, but not of starters. The cocultures exhibited more diverse functional outputs, such as texturing, production of flavour compounds, proteolysis, when the strains associated in coculture had distinct capacities. Appropriate associations of LAB and formulation offer interesting solutions to improve the perception of YAs, and ultimately, encourage their consumption.

Impact of lactic acid bacteria on the control of Listeria monocytogenes in ready-to-eat foods

Abstract Due to the increased demand for ready-to-eat (RTE) minimally processed foods, alternatives to chemical and thermal preservation methods to maintain food safety are highly demanded. A significant safety hazard in RTE food products is the growth of the foodborne pathogen Listeria monocytogenes (L. monocytogenes). After processing, recontamination or cross-contamination of L. monocytogenes in RTE food products may occur and the lack of cooking can lead to an increased risk of listeriosis. Further, some RTE food products (e.g. cheese and cured meat) can have a long processing period and shelf life, thus allowing for the growth and proliferation of L. monocytogenes in the food matrix. Lactic acid bacteria (LAB) are generally recognized as safe probiotics and have been proposed as a biological control approach to eliminate foodborne pathogens including L. monocytogenes. LAB have been reported to extend the shelf life of food products and inhibit pathogen proliferation via growth competition and metabolite production. LAB are native microflora of many RTE foods, but only certain LAB may inhibit pathogen growth. Therefore, the specificity of LAB species should be employed in their use in RTE foods. This review will discuss the antimicrobial mechanisms of LAB against L. monocytogenes, selective use of LAB in food matrices, and their uses in food processing and packaging.

Impact of lactic acid bacteria and enzymes on the fermentation processes of sugarcane tops silage at a particular time interval

The objective of this study was to achieve the virtuous fermentation quality of the sugarcane tops silage by combining the most promising additives with the day of ensiling. Fresh sugarcane tops were ensiled in 3-L laboratory silos with enzymes (Cellulase+ Xylanase), enzymes plus Lactobacillus plantarum (C+X+LP), enzymes plus Lactobacillus fermentum (C+X+LF) and enzymes +Lactobacillus plantarum + Lactobacillus fermentum (C+X+LP+LF) for 15, 25, 35, and 45 days. Urea (0.5%) and molasses (1.5%) were added in all treatment groups. After storage, the silages were subjected to microbial and chemical analyses. Results from the present investigation denoted that, fresh sugarcane tops had a low fermentation coefficient (

Secretome-Mediated Interactions with Intestinal Epithelial Cells: A Role for Secretome Components from Lactobacillus rhamnosus R0011 in the Attenuation of Salmonella enterica Serovar Typhimurium Secretome and TNF-α-Induced Proinflammatory Responses.

Recent evidence suggests that lactic acid bacteria communicate with host cells via secretome components to influence immune responses but less is known about gut-pathogen secretomes, impact of lactic acid bacteria secretomes on host-pathogen interactions, and the mechanisms underlying these interactions. Genome-wide microarrays and cytokine profiling were used to interrogate the impact of the Lactobacillus rhamnosus R0011 secretome (LrS) on TNF-α and Salmonella enterica subsp. enterica serovar Typhimurium secretome (STS)-induced outcomes in human intestinal epithelial cells. The LrS attenuated both TNF-α- and STS-induced gene expression involved in NF-κB and MAPK activation, as well as expression of genes involved in other immune-related signaling pathways. Specifically, the LrS induced the expression of dual specificity phosphatase 1 (DUSP1), activating transcription factor 3 (ATF3), and tribbles pseudokinase 3 (TRIB3), negative regulators of innate immune signaling, in HT-29 intestinal epithelial cells challenged with TNF-α or STS. TNF-α- and STS-induced acetylation of H3 and H4 histones was attenuated by the LrS, as was the production of TNF-α- and STS-induced proinflammatory cytokines and chemokines. Interestingly, the LrS induced production of macrophage migration inhibitory factor (MIF), a cytokine involved in host-microbe interactions at the gut interface. We propose that the LrS attenuates proinflammatory mediator expression through increased transcription of negative regulators of innate immune activity and changes in global H3 and H4 histone acetylation. To our knowledge, these findings provide novel insights into the complex multifaceted mechanisms of action behind secretome-mediated interdomain communication at the gut-mucosal interface.

Impact of Lactic Acid Bacteria on Dairy Animal’s Performance

Impact of Lactic Acid Bacteria on Dairy Animal’s Performance

The detoxification of aflatoxin M1 by Lactobacillus acidophilus and Bifidobacterium spp.: A review

One of the most studied mycotoxins is Aflatoxin M1 (AFM1), which as a carcinogen should be eliminated or limited from food products especially dairy products. Among different detoxification methods of AFM1, several strains of lactic acid bacteria (LABs) (particularly Lactobacillus acidophilus and Bifidobacterium spp.) can bind Aflatoxin M1 and furthermore, eliminate them. The principal mechanism of detoxification by LABs is the physical binding to peptidoglycan and polysaccharides present in the bacterial cell wall. This paper reviews the detoxification capability of some LABs strains and the critical roles of factors affecting the binding procedures including LAB strains, optimum incubation time, and the cell concentration of LABs. Practical application This study reviewed the impact of lactic acid bacteria on detoxification of aflatoxin M1. As the high toxicity effect of aflatoxin M1 in food is proved, finding a safe method in order to remove them is crucial. Lactic acid bacterias (LABs) are vastly applied in food science and technology due to their various beneficial effects, being easy manageable and safe technique. LABs were completely efficient in the elimination of aflatoxins in food besides having no potential adverse health/toxic effects.

Impact of Lactobacillus plantarum on thiol precursor biotransformation leading to production of 3-sulfanylhexan-1-ol

3-Sulfanylhexan-1-ol (3SH) is an important contributor to the fruity notes of wine. 3SH exists as odorless precursors in grape and its release from the precursors is generally mediated by yeast during alcoholic fermentation. Here, the impact of lactic acid bacteria on 3SH production was investigated. Among the species tested, only Lactobacillus plantarum released 3SH from S-3-(hexan-1-ol)-l-cysteine (3SH-S-cys) and S-3-(hexan-1-ol)-l-cysteinylglycine (3SH-S-cysgly) in the whole-cell biotransformation assay. The conversion yields of 3SH from 3SH-S-cysgly by L. plantarum were always higher than those from 3SH-S-cys, suggesting that the direct cleavage of 3SH-S-cysgly to yield 3SH predominantly occurred. L. plantarum biotransformed the 3SH precursors, including 3SH-S-glut, to release 3SH in fermented grape juice. The results indicate that L. plantarum induces the release of 3SH from the 3SH precursors. To the best of our knowledge, this is the first study showing the impact of L. plantarum on thiol precursor biotransformation.

The impact of lactic acid bacteria with antimicrobial properties on biodegradation of polycyclic aromatic hydrocarbons and biogenic amines in cold smoked pork sausages

The influence of surface treatment with lactic acid bacteria (LAB), previously cultivated in an alternative substrate, on the formation of polycyclic aromatic hydrocarbons (PAHs) and biogenic amines (BAs) in cold smoked pork meat sausages was investigated. Moreover, sausages treatment with LAB after the smoking on PAHs content changes was evaluated. Additionally, the inhibitory effects of LAB metabolites on food spoilage bacteria was determined using the agar well diffusion assay method. The metabolites of Pediococcus acidilactici KTU05-7, Pediococcus pentosaceus KTU05-9 and Lactobacillus sakei KTU05-6 strains showed good inhibitory properties against tested pathogenic and food spoilage bacteria. Moreover L. sakei produced bacteriocins inhibited the growth of Pseudomonas aeruginosa and Escherichia coli. Furthermore, the treatment of sausages surface with LAB before smoking decreased the content of cadaverine and spermidine, whereas the treatment of sausages surface with LAB after smoking decreased the content of putrescine (approx. 53% when L. sakei and P. acidilactici were applied) or totally eliminated (applying P. pentosaceus) from outer layers and centre of sausages. The application of LAB for sausages treatment before and after smoking significantly decreased both benzo[a]pyrene and chrysene decreasing (p < 0.05). The results also confirm that potatoes juice could be used as an alternative substrate for LAB cultivation, and the obtained fermented bioproducts could be applied for surface treatment of cold smoked pork sausages in case to reduce microbial contamination, and PAHs content in final product.

The effect of lactic acid bacteria fermentation on the antioxidant activity of wheat gluten pancreatin hydrolysates

SummaryThe antioxidant activities of the fermented wheat gluten hydrolysates with different fermentation times were investigated to elucidate the impact of lactic acid bacteria (LAB) fermentation on the wheat gluten hydrolysates. Prior to LAB fermentation, wheat gluten was deamidated by hydrochloric acid and then hydrolysed by pancreatin to 12 and 24 h, respectively. Results showed that LAB fermentation had significant impacts on the enzymatic efficiency and antioxidant activities of wheat gluten. The degree of hydrolysis and protein recovery of hydrolysates gradually increased and then reached maximum values, respectively, when fermenting with LAB for 36 h. The hydrolysis degree and protein recovery of fermented pancreatin 24‐h hydrolysates were larger than that of the fermented pancreatin 12‐h hydrolysates during the whole fermentation. The antioxidant activity analysis revealed a marked increase and improvement in the scavenging activities of 1,1‐Diphenyl‐2‐picrylhydrazyl·radicals, hydroxyl radicals and oxygen radical absorbance capacity, while the scavenging activities of ABTS+ radical decreased as the fermentation time extended. The antioxidant activities of pancreatin 24‐h hydrolysates were higher than that of the pancreatin 12‐h hydrolysates during the whole LAB fermentation.

Impact of lactic acid bacteria on oxidative DNA damage in human derived colon cells

It is assumed that reactive oxygen species (ROS) play a key role in inflammatory bowel diseases and colon cancer and a number of studies indicate that lactic acid bacteria (LAB) possess antioxidant properties and may prevent these diseases. In the present study, we developed a model which allowed us to investigate the prevention of oxidative DNA damage in human derived colon (HT29) cells by LAB. Furthermore, we investigated if these effects correlate with superoxide ( O 2 - ) resistance of the strains. The protective properties of 55 strains were monitored in single cell gel electrophoresis (SCGE) assays. After preincubation of the cells with LAB (60 min), oxidative damage was induced by exposure to plumbagin (5.0 μM, 120 min) which releases O 2 - or by hydrogen peroxide (50 μM, 10 min); O 2 - resistance was monitored in plate growth inhibition assays. 25 strains (45%) reduced plumbagin induced DNA migration while only few of them (20%) were protective towards hydrogen peroxide induced damage. The strongest effects (up to 60% reduction of O 2 - induced DNA migration) were observed with representatives of the species Streptococcus thermophilus. The prevention of DNA damage in the colon cells by the bacteria did not correlate with their O 2 - resistance. Additional experiments indicate that the reduction of oxidative damage is only seen with viable bacteria but not with heat inactivated cells and that it takes also place when the colon cells are separated from the LAB by permeable filter membranes indicating that the bacteria release ROS protective factors into the medium. Dose response experiments showed that the protection depends on the concentration of the bacteria; significant effects were observed with titers ⩾3 × 10 6−7 cells/ml. Unexpectedly, we found that a substantial fraction of the strains (13%) induced DNA damage in untreated cells, some of them increased also the effects of the ROS generating chemicals. Preliminary experiments with tetramethylbenzidine (TMB) agar indicate that this phenomenon may be due to release of hydrogen peroxide by the bacteria. Overall, our study shows that the impact of LAB on DNA damage in human derived colon cells is ambivalent; while the majority of strains was protective against oxidative damage some of them induced per se pronounced DNA migration. Since the effects were seen with bacterial concentrations which may be reached in the intestinal tract after consumption of fermented milk products, it is likely that the effects we observed in the present study are relevant for humans.

Impact of Lactic Acid Bacteria on Dendritic Cells from Allergic Patients in an Experimental Model of Intestinal Epithelium

Lactic acid bacteria (LAB) are Gram positive nonpathogenic commensal organisms present in human gastrointestinal tract. In vivo, LAB are separated from antigen-presenting cells such as dendritic cells (DC) by the intestinal epithelial barrier. In this study, the impact of one LAB strain (Lactobacillus casei ATCC393) on human monocyte-derived DC from allergic and healthy donors was assessed by using a polarized epithelium model. Confocal and flow cytometer analyses showed that immature DC efficiently captured FITC-labelled L. casei through the epithelial layer. After interaction with L. casei, DC acquired a partial maturation status (i.e., CD86 and CD54 increase) and increased their interleukin (IL)-10 and IL-12 production. Interestingly, after activation by L. casei in the presence of experimental epithelium, DC from allergic patients instructed autologous naïve CD4+ T cells to produce more interferon-γ than without the epithelium. Thus by modulating human DC reactivity, LAB and intestinal epithelium might modify T cell immune response and regulate the development of allergic reaction.

The impact of lactic acid bacteria on sourdough fermentation

The baking of sourdough breads represents one of the oldest biotechnological processes. Despite traditionality, sourdough bread has great potential because of its benefits. Sourdough is a mixture of flour and water that is dominated by a complex microflora composed of yeasts and lactic acid bacteria that are crucial in the preparation of bread dough. Lactic acid bacteria cause acidification by producing lactic acid that increases the shelf life of bread by preventing the growth of undesirable microorganisms and affects the nutritional value of bread by increasing the availability of minerals. In addition to these advantages, the use of sourdough fermentation also improves dough machinability, breadcrumb structure and the characteristic flavour of bread. Lactic acid bacteria in sourdough fermentation are well known representing both homofermentative and heterofermentative bacteria. They may originate from selected natural contaminants in the flour or from a starter culture containing one or more known species of lactic acid bacteria. Sourdough can be cultivated in bakeries or obtained from commercial suppliers. However, many bakeries in Europe still use spontaneously fermented sourdoughs, which have been kept metabolically active for decades by the addition of flour and water at regular intervals. The impact of lactic acid bacteria on sourdough fermentation and their influence on dough and bread quality was discussed on the basis of research and literature data.

Lactic acid bacteria and the human gastrointestinal tract.

This review summarises the effects of lactic acid bacteria on lactose malabsorption, bacterial/viral or antibiotic associated diarrhoea, and describes the impact of lactic acid bacteria on cancer and the fermentative products in the colon. Eight studies (including 78 patients) demonstrated that lactase deficient subjects absorbed lactose in yogurt better than lactose in milk, while two studies (25 patients) did not support this. Two studies (22 patients) showed that unfermented acidophilus milk was absorbed better than milk, while six studies (68 patients) found no significant differences. Addition of lactose hydrolysing enzyme, lactase, to milk improved lactose malabsorption in seven studies (131 lactose malabsorbers), while one study (10 malabsorbers) demonstrated no improvement. Lactic acid bacteria alleviated travellers' diarrhoea in one study (94 individuals) while a study including 756 individuals was borderline statistically significant. One study (50 individuals) did not find an effect of lactic acid bacteria on travellers' diarrhoea. Six studies (404 infants) demonstrated a significant effect of lactic acid bacteria on infant diarrhoea, while one study (40 infants) did not. Lactic acid bacteria moderated antibiotic associated diarrhoea in three studies (66 individuals), while two studies (117 individuals) were insignificant. Lactase deficient subjects benefit from a better lactose absorption after ingestion of yoghurt compared with milk and from milk added lactase, whereas ingestion of unfermented acidophilus milk does not seem to improve lactose absorption. The majority of studies support that lactic acid bacteria alleviate bacterial/viral induced diarrhoea, especially in infants, while the effect on antibiotic associated diarrhoea is less clear. Experimental studies indicate an effect of lactic bacteria on human cell cancer lines, but clinical evidence is lacking. A 'stabilising' effect of lactic acid bacteria on the colonic flora has not been documented.