Thermophilic lactic acid bacteria

Dyachenko, P. F., Shchedushnov, E. V. and Nassib, T. G. 1970. Characteristics of proteolytic activity of thermophilic lactic acid bacteria used for cheesemaking. XVIII Int. Dairy Congr. IE, 274. 

Vallea, E. and Mocquot, G. 1968. Preparation of a concentrated suspension of thermophilic lactic acid bacteria for use in cheesemaking. Lait 48, 631-643. (French)... 

Bacterial spoilage at various stages in the brewing process The spoilage caused by bacteria at the various stages of the brewing process are outlined in Table 21.2. The infection of sweet-wort by thermophilic lactic acid bacteria has already been mentioned. Because these bacteria are sensitive to isohumulones, they do not survive in hopped wort. 

Cerning, J., Bouillane, C., Landon, M. and Desmazeaud, M.J. (1990) Comparison of exocellular polysaccharide production by thermophilic lactic acid bacteria. Sciences des aliments 10(2), 443-451. 

The production of yoghurt is presented schematically in Fig. 10.21. Yoghurt cultures consist of thermophilic lactic acid bacteria that live together symbiotically (Streptococcus thermophilus and Lactobacillus bulgaricus). Incubation is conducted on addition of 1.5-3% of the operating culture at 42-45 °C for about 3 h. The final product has a pH value of about 4-4.2 and contains 0.7-1.1% of lactic acid. Functional foods include yoghurts which have been incubated with probiotics. Probiotics are defined, cultured strains of lactic acid bacteria, which have been isolated from human intestinal flora, e. g., certain lactobacilli and bifidobacteria. On consumption, they are supposed to reach the large intestine and contribute to the formation of an optimal intestinal flora. 

On storage, beer can become cloudy and form a sediment. Proteins and polypeptides make up 40-75% of the turbidity-causing solids. They become insoluble due to the formation of inter-molecular disulfide bonds, complex formation with polyphenols, or reactions with heavy metals ions (Cu, Fe, Sn). Other components of the sediment are carbohydrates (2-25%), mainly a- and P-glucans. For measures used to prevent cloudiness, see 20.1.8.5. Undesirable microorganisms, e. g., thermophilic lactic acid bacteria, acetic acid bacteria Acetobacter, Gluconobacter) and yeasts, can cause disturbances and defects in various process steps (mashing, fermentation, finished product). 

Sudrez, V.B., Quiberoni, A., Binetti, A.G., and Reinheimer, J.A. (2002) Thermophilic lactic acid bacteria phages isolated from Argentinean dairy industries. J Food Prot 65, 1597-1604. 

Falentin, H., Henaff, N., Le Bivic, P, et al. (2012) Reverse transcription quantitative PCR revealed persistency of thermophilic lactic acid bacteria metabolic activity until the end of the ripening of Emmental cheese. Food Microbiol... 

Mozzi, F., Oliver, G., Savoy de Giori, G. Font de Valdez, G. F. (1995). Influence of temperature on the production of exopolysaccharides by thermophilic lactic acid bacteria. Milchwissensaft, 50, 80-82. 

Catalases catalyze the conversion of hydrogen peroxide to dioxygen and water. Two families of catalases are known, one having a heme cofactor and the second a structurally distinct family, found in thermophilic and lactic acid bacteria. The manganese enzymes contain a binuclear active site and the functional form of the enzyme cycles between the (Mn )2 and the (Mn )2 oxidation states. When isolated, the enzyme is in a mixture of oxidation states including the Mn /Mn superoxidized state and this form of the enzyme has been extensively studied using XAS, UV-visible, EPR, and ESEEM spectroscopies. Multifrequency EPR and microwave polarization studies of the (Mn )2 catalytically active enzyme from L. plantarum have also been reported. ... 

In addition to baker s yeast, several systems that selectively reduce aliphatic ketones are now known. Lactic acid bacteria, e.g., Lactobacillus fermentum, Lactobacillus brevis or Leuconostoc paramesenteroides, reduce 2-pentanone or acetophenone in high yield (50- 100%) and high enantioselectivity (94-100% ee) to the (S )-configurated alcohols247. (5)-Alcohols are also obtained with high enantiomeric excess from 2-pentanone, 2-heptanone, 2-octanone and the substituted ketones 3-methyl-2-butanone and 4-methylpentane-2,3-dione by reduction with resting cells of the thermophilic archaebacterium Sulfolobus so/fataricus24s. 

Many names have been assigned to the lactic acid bacteria associated with brewing. It is probable however that most rod-shaped isolates may be classified as the heterofermentative species Lactobacillus brevis, the homo-fermentative species . casei and L, plantarum, and the homofermentative thermophilic species L. delbrueckii [14]. Cocci are also encountered, notably the homofermentative Pediococcus damnosus. (Less common because they are more sensitive to hop resins are P. pentosaceuslacidilactici. Streptococcus saprophyticus, S. epidermis and Micrococcus varians.) Micrococcus kristinae is however resistant to hop resins and low pH, but requires oxygen for growth [15]. An American report states that many breweries encounter L. brevis, L. plantarum and P. damnosus. When the primary fermentation is complete, Pediococcus continues to grow at the bottom of the fermenter in the deposited yeast [16]. 

Recently, a change from the traditional anaerobic fermentation to an aerobic respiration process has been introduced for Lactococcus spp. The lactic acid bacteria exhibit a respiratory lifestyle in the presence of oxygen and heme. Consequences of the respiration are the higher biomass and lower amount of lactic add produced. However, the aeration and heme did not increase the biomass yield of Streptococcus thermophiles, L. delbrueckii subsp. bulgaricus, or L. helveticus (Pedersen, Iversen, Sorensen, Johansen, 2005). 

Dozens of different peptides have been identified in cheeses. Most of them arise from and -caseins and a few are from aj2-and K-caseins. The proteinases involved in hydrolysis of aj -casein are mainly cathepsin D originating from milk and cell-envelope proteinase from thermophilic starters, while P- and aj2-caseins are mainly hydrolysed by plasmin. Moreover, peptidases from starters are also active throughout the ripening process, presumably similar to those from non-starter lactic acid bacteria. For example, the bitterness of mature Gouda cheese is caused by calcium and magnesium chlorides, some bitter-tasting free amino acids and is modified by peptides, which arise from the hydrolysis of fS-casein (such as decapeptide Tyr-Pro-Phe-Pro-Gly-Pro-Ile-His-Asn-Ser and derived nonanpeptide without the terminal serine) and casein (tetrapeptide Leu-Pro-Gln-Glu). 

Patel, M. A., Ou, M., Harbrucker, R., Aldrich, H., Buszko, M., Ingram, L., and Shanmugam, K. 2006. Isolation and characterixation of acid-tolerant, thermophilic bacteria for effective fermentation of biomass-derived sugars to lactic acid. Appl. Environ. Microbiol., 72, 3228-3235. 

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