Browsing by Subject "Lactobacillus"

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    Backmittel mit fermentativ angereicherten Hydrokolloiden
    (2021) Seitter, Michael Friedrich Hermann; Hertel, Christian
    Lactic acid bacteria (LAB) are involved in fermentation of sourdoughs and able to produce exopolysaccharides (EPS). Screening of 190 LAB of different species and genera showed that 82% are able to produce EPS. Whereby, 28% a strong or very strong production exhibited. It becomes evident that strains of species L. reuteri, L. sanfranciscensis, L. frumenti and L. pontis, could be identified as effective EPS producer. The molecular weight of the synthetized EPS was larger than 5*106 Dalton. Glucan was formed almost of L. reuteri strains. To identify the effect of commercial hydrocolloids on bread staling, baking trials were performed. The parameter crumb hardness using Texture-Profile-Analysis and retrogradation of starch using Differential Scanning Calorimetry were chosen. Staling of wheat breads was dependent on the flour quality. Breads produced using weak flours and straight dough method showed faster staling. Addition of isolated EPS produced by L. sanfranciscensis LTH 1729 (Glu/Fru ratio: 1:6) and LTH 2590 (Glu/Fru ratio: 1:45) was more effective in retarding the rate of staling compared to hydrocolloids guar gum and xanthan. Baking trials with chemical acidified sponges showed that swelling and endogenous enzyme activities exerts no positive effect on the rate of staling. In contrast to sponges with fermentative enriched EPS, which exhibits a delayed rate of staling. This effect could be verified in mixed wheat breads (rye : wheat, 50:50). Frozen storage of doughs revealed no influence on the rate of staling. Production of an EPS enriched dried sourdough (baking improver) using optimized fermentation conditions was performed using L. sanfranciscensis LTH 1729. 3% dosage of the baking improver showed similar staling rate compared to control, however with 2% higher water absorption. Thus, addition of hydrocolloids and EPS, respectively, leads to an increase in dough yield of 1 1.5%. The width-height ratio was comparable in all doughs, except the xanthan supplemented. After adjusting the doughs to 500 FE, all doughs showed similar results in measurements with Bohlin-Rheometer. Doughs with added hydrocolloids as well as EPS were less sticky. Fermented sponge doughs with enriched EPS showed higher stickiness compared to not enriched. This could be traced back to residual not metabolized amounts of sucrose. EPS addition affects extensibility of doughs less compared to gum guar and xanthan. Negative influence on dough structure using acidic sponges was compensated with EPS enriched ones. Addition of guar gum and xanthan effect in a viscosity increase during gelatinization. Whereas, EPS and EPS containing sponges showed no effect on viscosity. Frozen storage of 10 days reveals lower dough stability and gas retention. Doughs were less elastic and stickier. Dough resistance decreased and elasticity increased. By addition of EPS these effects could be compensated. The gas retention capability of EPS supplemented frozen doughs was identical not frozen ones. Addition of 3% baking improver produced by spray dried EPS enriched sourdough to doughs increased the water absorption by 2%, whereas almost no change on dough rheological parameters resulted. Dough stability and gas retention was considerably improved. Dough stickiness and resistance decreased. No effect in viscosity during gelatinization. Summarized, the results of the present work show the optimization and manufacturing of a “clean label” baking improver, produced thru EPS enriched fermentation of sourdoughs. As well as the application of the improver and the impact of on dough processing and fresh keeping of frozen dough and baked goods.
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    Comparison of aqueous and lactobacterial-fermented Mercurialis perennis L. (Dog’s Mercury) extracts with respect to their immunostimulating activity
    (2023) Lorenz, Peter; Zilkowski, Ilona; Mailänder, Lilo K.; Klaiber, Iris; Nicolay, Sven; Garcia-Käufer, Manuel; Zimmermann-Klemd, Amy M.; Turek, Claudia; Stintzing, Florian C.; Kammerer, Dietmar R.; Gründemann, Carsten
    Lactic acid (LA) fermentation of dog’s mercury (M. perennis L.) herbal parts was investigated in samples inoculated with either Lactobacteria (Lactobacillus plantarum and Pediococcus pentosaceus, LBF) or whey (WF). Depending on fermentation time, LA concentrations were monitored in a range of 3.4–15.6 g/L with a concomitant pH decline from 6.5 to 3.9. A broad spectrum of cinnamic acids depsides containing glucaric, malic and 2-hydroxyglutaric acids along with quercetin and kaempferol glycosides were detected by LC-DAD-ESI-MSn. Moreover, in this study novel constituents were also found both in unfermented and fermented extracts. Furthermore, amino acids and particular Lactobacteria metabolites such as biogenic amines (e.g., putrescine, 4-aminobutyric acid, cadaverine) and 5-oxoproline were assigned in WF extracts by GC-MS analysis after silylation. Enhanced NFκB and cytokine expression (IL-6, TNFα, IL-8 and IL-1β) was induced by all extracts, both non-fermented and fermented, in NFκB-THP-1 reporter cells, showing a concentration-dependent immunostimulatory effect. The WF extracts were tested for micronuclei formation in THP-1 cells and toxicity in luminescent bacteria (V. fischeri), whereby no mutagenic or toxic effects could be detected, which corroborates their safe use in pharmaceutical remedies.
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    Ecological studies of the Lactobacillus biota in the human digestive tract and adaptation of intestinal lactobacilli to the sourdough ecosystem
    (2005) Dal Bello, Fabio; Hertel, Christian
    Among the bacteria inhabiting the human gut, lactobacilli have received considerable attention, due to their putative health promoting effects (Reid, 1999; Vaughan et al., 1999). Cultivation of lactobacilli is considered to be reliable and numerous studies using plating on selective media have been performed to investigate these bacteria in intestinal ecosystems (Tannock, 1995; Reuter, 2001). Recently, the application of PCR-DGGE in combination with primers specific for lactic acid bacteria (LAB) detected species which are not considered to be intestinal inhabitants but food-associated, such as Lactobacillus curvatus, Lactobacillus sakei, Leuconostoc mesenteroides and Pediococcus pentosaceus (Walter et al., 2001; Heilig et al., 2002). Remarkably, these species could not be recovered by traditional bacteriological culture on Rogosa SL agar (Walter et al., 2001). In Chapter III, different cultivation media, as well as new incubation conditions were applied to overcome these difficulties. Human faecal samples were plated on selective and non-selective media and incubated under standard condition (37°C, anaerobiosis) for faecal LAB as well as alternative condition (30°C, 2% O2). PCR-DGGE analyses of resuspended bacterial biomass (RBB) obtained from agar plates revealed that the species composition of the recovered LAB was affected stronger by the incubation condition than by the used medium. It was observed that food-associated LAB such as L. sakei and Lc. mesenteroides, hitherto not described as intestinal inhabitants, are more easily selected when the alternative incubation condition is used. Identification of randomly picked colonies grown under the alternative condition on Rogosa SL agar showed that L. sakei is one of the predominant food-associated LAB species in faecal samples, reaching counts of up to 106 CFU per gram faeces. Comparison of the results of bacteriological culture with those obtained by PCR-DGGE analysis of the RBB showed that investigation of RBB is a fast and reliable method to gain insight into the species composition of culturable LAB in faeces. Examination of the faecal Lactobacillus populations over longer periods has revealed marked variation in the complexity and stability of these populations among human subjects (Vanhoutte et al., 2004, Walter et al., 2001). Ecological studies indicate that most Lactobacillus species found in the human gastrointestinal tract (GIT) are likely to be transient (allochthonous), originating from either the oral cavity or food (reviewed in Bibiloni et al., 2004). In order to investigate if oral lactobacilli constitute a part of the faecal Lactobacillus biota, the Lactobacillus biota of saliva and faeces of three human subjects were investigated and compared at two time-points in a three months interval (Chapter IV). The species composition of the Lactobacillus biota of human saliva and faeces was found to be subject-specific and fluctuated to some degree, but the species Lactobacillus gasseri, Lactobacillus paracasei, Lactobacillus rhamnosus and Lactobacillus vaginalis were detected at both time-points in saliva and faecal samples of individual subjects. RAPD-PCR analysis indicated that several strains of these species were present both in the oral cavity and in the faecal samples of the same subject. Oral isolates of the species L. gasseri and L. vaginalis showing identical RAPD types were found to persist over time, suggesting that these species are autochthonous to the oral cavity. The results of Chapter IV, together with recently published data (reviewed in Bibiloni et al., 2004), give strong evidence that some lactobacilli found in human faeces are allochthonous to the intestine and originate from the oral cavity. Lactobacilli have been detected in diverse environments and have been the subject of considerable research due to their commercial use in the food industry (reviewed in Hammes and Hertel, 2003). Several Lactobacillus species are commonly detected in both fermented food and the human GIT, but the genetic background for this ecological versatility is poorly understood. Lactobacillus reuteri is a dominant member of the microbiota of type II sourdough fermentations (Meroth et al., 2003) and is considered one of the truly autochthonous Lactobacillus species in humans (Reuter, 2001). The in vivo expression technology (IVET) developed by Walter et al. (2003) was used to identify genes (so-called ivi genes) of the sourdough isolate L. reuteri LTH5531 that show elevated levels of expression during growth of this organism in a type II sourdough fermentation (Chapter V) and during passage through the GIT of mice (Chapter VI). Thirty-eight induced fusions were found to be highly expressed during the sourdough fermentation (Chapter V), and 29 genes could be identified on the basis of the available sequence information. Four genes encoded stress-related functions (e.g. acid and general stress response) reflecting the harsh conditions prevailing during sourdough fermentation. Further eight genes were involved in acquisition and synthesis of amino acids and nucleotides, indicating their limited availability in sourdough. The remaining genes were either part of functionally unrelated pathways or encoded hypothetical proteins. The identification of a putative proteinase and a component of the arginine deiminase pathway are of technological interest, as they are potentially involved in the formation of aroma precursors. Remarkably, IVET with the genomic library that was successfully used in the sourdough study (Chapter V) did not detect ivi promoters when LTH5531 inhabited the GIT of mice (Chapter VI). With IVET, active promoters are selected by expression of an "essential growth factor" (in our system the erythromycin resistance mediated by ErmGT) that allows the organism to colonize and/ or grow in the ecosystem (Rainey, 1999, Walter et al., 2003). Expression of ivi promoters in particular ecosystems must therefore be permanent and strong in order to allow comparable growth rates of ivi clones and clones bearing constitutive promoters, especially in the GIT, where inactive bacteria are washed out. The findings of Chapter V and VI indicate that L. reuteri LTH5531 does not possess strongly expressed "GIT inducible" genes, while possessing 38 ones specifically induced in sourdough. Ivi genes are more likely to contribute to the ecological performance of an organism in a specific environment than genes expressed equally in a broad range of habitats (Rainey, 1999, Gal et al, 2003, Walter et al., 2005). Therefore, traits encoded by ivi genes are likely to be adaptive and the extent of their expression would be shaped by natural selection to improve ecological fitness. The presence of thirty-eight "sourdough specific" ivi fusions in L. reuteri LTH5531 probably reflects the long term adaptation of LTH5531 to the sourdough environment, just as ivi genes detected in strain 100-23 reflect adaptation of this GIT isolate to the rodent GIT (Walter et al., 2003). Indeed, LTH5531 was isolated from an experimental sourdough that had been inoculated with an industrial starter. This industrial starter has been propagated over several years, giving the organisms present sufficient time to adapt. In accordance with this, by using RAPD-PCR, Meroth et al. (2003) showed that strain LTH5531 was present in a commercial type II sourdough starter collected 10 years prior isolation of LTH5531, thus indicating that this strain has adapted to the sourdough environment for at least 10 years. The results of Chapter V clearly demonstrated that knowledge of gene expression and metabolic activities of bacteria during food fermentations can be obtained by applying IVET. The results collected provide an important molecular basis on which improved starter strains can be developed for industrial exploitation. Moreover, the results of Chapter VI show the importance of working with highly adapted, autochthonous strains in studies of microbial ecology in order to reveal the adaptive interactions responsible for the ecological success of these bacteria in their natural environment or during food fermentations.
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    Food-grade Lactobacilli expression systems for recombinant enzymes
    (2013) Böhmer, Nico; Fischer, Lutz
    Lactobacilli are Gram-positive bacteria used throughout the food industry as traditional starters for various fermented foods. Lactobacilli would be superior for recombinant enzyme production regarding the food safety demands since most of them are Generally Recognised As Safe (GRAS) organisms. The major advantages of Lactobacilli as food-associated microorganisms used for recombinant enzyme production are their safe and sustainable use as overall safety food-grade expression systems. In the work presented, Lactobacilli were studied in detail as food-grade expression systems for recombinant enzyme production. In a first analysis, the two pSIP expression systems, pSIP403 and pSIP409, were investigated to produce a hyper-thermophilic Beta-glycosidase (CelB) from Pyrococcus furiosus in Lactobacillus plantarum NC8 and Lactobacillus casei as hosts, respectively. Both Lactobacilli harbouring the pSIP409-celB vector produced active CelB in batch bioreactor cultivations, while the specific CelB activity of the cell-free extract was about 44% higher with Lb. plantarum (1,590 ± 90 nkatpNPGal/mgprotein) than with Lb. casei (1,070 ± 66 nkatpNPGal/mgprotein). A fed-batch bioreactor cultivation of Lb. plantarum NC8 pSIP409-celB resulted in a specific CelB activity of 2,500 ± 120 nkatpNPGal/mgprotein. A basal whey medium with supplements was developed as an alternative to the cost intensive MRS medium used. About 556 ± 29 nkat pNPGal/mgprotein of CelB activity was achieved in bioreactor cultivations using this medium. It was shown that both Lactobacilli were potential expression hosts for recombinant enzyme production. An additional approach was performed to produce a metagenome-beta-galactosidase using Lb. plantarum NC8 with the pSIP expression system. Using this system, a quite low maximal galactosidase activity of only 0.18 nkatoNPGal/mgprotein was detected. A 13 times higher activity of 2.42 nkatoNPGal/mgprotein was produced after the knock out of the interfering native Kluyveromyces lactis Beta-galactosidase in the well-known food-grade K. lactis pKLAC2 expression system. Nevertheless, the best performing expression system for the recombinant production of the metagenome-derived enzyme was the Escherichia coli BL21 strain with a pET vector, resulting in the highest Beta-galactosidase of 82.01 nkatoNPGal/mgprotein. Beside the use of the pSIP expression system, a novel expression system for Lb. plantarum was developed. This system is based on the manganese starvation-inducible promoter from the specific manganese transporter of Lb. plantarum NC8 which was cloned for the first time. The expression of CelB was achieved by cultivating Lb. plantarum NC8 at low manganese concentrations with MRS medium and the pmntH2-celB expression vector. A CelB activity of 8.52 µkatoNPGal/L was produced in a bioreactor. The advantages of the novel expression system are that no addition of an external inducing agent was required, and additionally, no further introduction of regulatory genes was necessary. The new promoter meets the general demands of food-grade expression systems. The glutamic acid racemase of Lb. plantarum NC8 was cloned and characterized in this work for the first time as a possible target for a food-grade selection system for this species. Glutamic acid racemases (MurI, E.C. 5.1.1.3) catalyse the racemisation of L- and D-glutamic acid. MurIs are essential enzymes for bacterial cell wall synthesis, which requires D-glutamic acid as an indispensable building block. Therefore, these enzymes are suitable targets for antimicrobial drugs as well as for the potential design of auxotrophic selection markers. A high expression system in E. coli BL21 was constructed to produce and characterize the biochemical properties of the MurI from Lb. plantarum NC8. The recombinant, tag-free Murl was purified by an innovative affinity chromatography method using L-glutamic acid as the relevant docking group, followed by an anion exchange chromatography step (purification factor 9.2, yield 11%). This two-step purification strategy resulted in a Murl sample with a specific activity of 34.06 µkatD-Glu/mgprotein, comprising a single protein band in SDS-PAGE. The purified Murl was used for biochemical characterization to gain in-depth knowledge about this enzyme. Only D- and L-glutamic acid were recognised as substrates for the Murl with similar kcat/Km ratios of 3.6 sec-1/mM for each enantiomer. The findings in this study may contribute to further development and implementation of food-grade Lactobacilli expression systems for recombinant enzyme production. Furthermore, the results obtained may help to optimise and select hosts and expression systems for industrial enzyme production for the needs of the food industry.
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    Mikrobiologische und biochemische Analyse der Fermentationseigenschaften von Lactobacillus paralimentarius AL28 und Lactobacillus plantarum AL30 in Sauerteigen aus Pseudozerealien
    (2011) Vogel, Antje; Schmidt, Herbert
    Pseudocereals are absent of gluten and therefore are important for people having a gluten-intolerance. Today no commercial starter cultures are available for sourdough fermentations with pseudocereals. This PHD-Thesis shows results of the characterisation of L. paralimentarius AL28 and L. plantarum AL30 concerning an application in pseudocereal sourdoughs. The fermentation properties of the strains, applied as single strains and in combination, were assessed in laboratory scale fermentations with amaranth and buckwheat. The fermentation studies were performed with a dough yield of 200 and over a period of two to ten days at 30°C with daily refreshment step. The investigated strains acidified the sourdoughs fast within the first two propagation steps as single strains as well as in combination (approximately pH 4). In amaranth higher total titratable acidity (TTA) -values (TTA between 25 and 30) were measured than in buckwheat (TTA of 20). 16S rDNA / 28S rDNA-PCR sequencing and RAPD-PCR were applied to determine the bacterial and eucaryotic species affiliation, respectively, and to trace specific strains during the fermentation process. The analysed strains competed against the autochthonous microbiota with the result of suppression the majority of yeasts and moulds as well as strains of their own species within the first 12 h of sourdough fermentation. They also suppressed an autochthonous microbiota grown up to 10^8 cfu/g sourdough. Single strains as well as the combination of both strains dominated the microflora in all tested flours / fermentation batches. Both strains displayed reproducible results concerning their over-all fermentation characteristics. L. paralimentarius AL28 and L. plantarum AL30, respectively, dominated the LAB viable counts in all flours after 10 days of fermentation as single strains (>/= 68 % and >/= 98 % of LAB, respectively) as well as in combination. In the latter case strain L. plantarum AL30 was especially competitive in buckwheat (AL28:AL30 = 1:1), more than in amaranth (AL28:AL30 = 4:1). The strains were characterised by their short lag-phase of
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    Molecular characterization of the interaction of lactobacilli with food environments and enterohemorrhagic Escherichia coli O157:H7
    (2009) Hüfner, Eric; Hertel, Christian
    The first part of this thesis focuses on the gene expression of Lactobacillus sakei and Lactobacillus reuteri in food fermentation using in vivo expression technology (IVET) and DNA microarray hybridization analysis, respectively. Both technologies allow the identification of regulated genes in a specific environment, which are likely to contribute to the ecological performance of the organism. Thus, the obtained results provide a basis for the development of new strategies to improve the fermentation process, as it was demonstrated by the development of an efficient method for the improvement of sausage fermentation using L. sakei. To obtain hygienically safe products, the function of starter cultures mostly relies on the ability to acidify and produce other antimicrobial principles. However, it was recently demonstrated that the interaction with pathogens also can take place on another level, apart from killing or growth inhibition. Lactobacilli have been shown to influence the virulence gene expression of enterohemorrhagic Escherichia coli (EHEC) via the bacterial communication system termed quorum sensing. The second part of the thesis explores the impact of quorum sensing between Lactobacillus reuteri strains and EHEC O157:H7 on EHEC virulence gene expression. By using a green fluorescent protein reporter gene assay, it was demonstrated for the first time that the transcription of the ler virulence regulator gene is significantly reduced by secreted substances of L. reuteri in a strain- and quorum sensing-dependent manner.
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    New approaches in salami manufacture with in-situ exopolysaccharide-forming starter cultures
    (2021) Velasco Cucaita, Lina Maria; Weiss, Jochen
    Lactic acid bacteria have always been of great importance in the production of fermented sausages such as salami, as they contribute not only to microbial stability but also to acidity and flavor profiles of such products. Recently, exopolysaccharide (EPS)-forming starter cultures have attracted the interest of the food industry. EPS have water-binding, gelling, viscosity-increasing, as well as emulsifying properties and, due to these technofunctionalities, can contribute to the improvement of existing products as well as to new product developments. However, compared to hydrocolloids, which have similar functionalities, in-situ formed EPS do not have to be legally declared as ingredients on a package. Initial studies looking at the use of such cultures in spreadable, short-ripened raw sausages showed that the use of EPS-forming starter cultures can lead to a significant improvement in the spreadability of fat-reduced tea sausage and deeper acidified onion mettwurst (pH 5.1 instead of 5.6). However, no study to date has comprehensively addressed the use of in-situ EPS-forming starter cultures in sliceable, raw fermented sausage products such as salami, which differ significantly from spreadable raw sausage products in terms of product matrix. Since growth kinetics and acidification depend on the microorganism and the food matrix used, the growth and acidification behavior of selected homo- and heteropolysaccharide (HePS)-forming lactic acid bacteria as a function of different sugar concentrations (2.5 - 10 g/kg) was initially investigated. This was done to obtain an indication of the sugar concentration required in the raw sausage mass to achieve a target pH of 4.8-5.3 in the final product. Subsequently, the performance of two HePS-producing strains L. plantarum TMW 1.1478, and 1.25; and the two homopolysaccharide-producing lactic acid bacteria L. curvatus TMW 1.624 and L. sakei TMW 1.411 was investigated in a raw sausage model system (inoculation concentration 106 CFU/g), which, in addition to 25% pork back fat, 75% lean pork meat, also contained ascorbic acid (0.5 g/kg), nitrite curing salt (28 g/kg), and dextrose or sucrose (5 g/kg). Thereby, the strains to be used were specifically analyzed with regard to their suitability for EPS-formation under typical fermentation conditions prior to use in salami production. The latter was done qualitatively by confocal laser microscopy (CLSM), followed by semi-quantitative data interpretation using MATLAB. The results showed that all selected strains were able to produce EPS in the raw sausage model matrix. There, EPS were located on the surfaces of the proteins. Since presence of HePS, which are more complex in terms of chemical structure and are often charged, can lead to changes in the organization of protein matrices even when used in very small amounts due to e.g. electrostatic interactions, sausages were subsequently prepared with a HePS-forming (L. plantarum 1.1478) and a non-EPS-forming starter culture (L. sakei 1.2037; control). Moreover, the influence of different inoculation concentrations (107 and 109 CFU/g) on fermentation and associated HePS-formation, as well as their effect on quality parameters of the final products, were investigated. The selection of inoculation concentrations was governed by the hypothesis that higher inoculation concentrations could lead to a higher in-situ formed HePS amount in the raw sausage matrix and therefore to enhanced structural and thus organoleptic relevant effects. For this purpose, pork meat and fat-based raw sausages were prepared by adding and mixing spices, 0.5 g/kg Na-ascorbate, 5 g/kg sugar, the appropriate starter culture (107-109 CFU/g), and in the end 28 g/kg nitrite curing salt. Afterwards, the mass was filled, fermented (24 °C), smoked, and dried to a weight loss of 31%. In addition to pH and bacterial plate counts, the formed EPS were detected by CLSM and the influence of the formed HePS on the texture of the raw sausages was analyzed by texture profile analysis (at 16, 23, 27, and 31% weight loss) and further evaluated in a sensory evaluation for the attributes of consistency and taste. Although no significant differences were found with respect to the detected HePS and the inoculation concentration used, dependencies emerged with respect to product quality. Raw sausages produced with the HePS-producing starter culture L. plantarum 1.1478 were significantly (p < 0.05) softer than the corresponding control samples. This effect was more pronounced the higher the inoculation concentrations, which was also reflected in the sensory evaluation of samples. Semi-quantitative data interpretation of the CLSM images revealed that the HePS were predominantly formed during the first 72 h of fermentation at 24 °C, until the final pH of 4.95 ± 0.05 was reached. Although there was no clear preference in the sensory analysis performed, raw sausages with a firmer consistency are generally preferred in Germany. Accordingly, the use of an EPS-forming culture could, depending on the market, also have a negative impact on product properties. To gain a better understanding of the observed results and the influence of process conditions on in-situ HePS-formation and its effects on the quality of sliceable raw fermented sausages, the temperatures of the fermentation phase were varied in a further study. In addition to the 24 °C already examined, an additional incubation temperature of 16 °C, commonly used in the production of raw sausages, and a low temperature incubation of 10 °C were chosen, since increased stress conditions are often associated with increased EPS formation. Raw sausages inoculated with L. plantarum 1.1478 or L. sakei 1.2037 (108 CFU/mL) were fermented at 10, 16, or 24 °C within the first 7 days and then dried under the same conditions (14 °C, controlled relative humidity) until a weight loss of 31% was reached. Microbial growth, pH, and weight loss development were monitored, EPS detected with CLSM, and products further characterized by texture profile analysis and a sensory test. Here, texture profile analysis was performed not only from the final product, but also after 21% and 26% weight loss to better understand the influence of the in-situ produced HePS. Differences were found depending on the starter culture used as well as on the fermentation temperature. Products manufactured with the non-EPS-forming strain L. sakei 1.2037 reached the target weight loss of 31% slightly faster than products manufactured with the HePS-former L. plantarum 1.1478. In both products, the final weight loss of 31% was reached faster at an initial fermentation temperature of 24 °C than at the lower fermentation temperatures. A correlation of temperatures with the amount of HePS formed could not be conclusively proven using semi-quantitative data analysis of CLSM images because matrix effects complicated the determination. However, texture profile analysis results showed a difference between products fermented at 24 °C and those fermented at cooler temperatures. In addition, significant (p < 0.05) differences were again observed between products with (softer) and without (harder) HePS-forming starter cultures at weight losses at or above 21%. These results were confirmed in the final sensory evaluation of the products (pH 4.89 - 5.01; 31% weight loss). In summary, the results of this thesis show that the use of a HePS-forming starter culture in sliceable raw fermented sausage can induce specific structural and textural changes. HePS-formation and associated quality attributes may be modulated via the inoculation concentration and control of processing parameters such as fermentation temperature. The texture softening observed in the present work, can be positively or negatively associated with the product depending on the target country and market. Taken together, results of this work underline the importance of a suitable starter culture selection for the production of fermented sausages.