Lactic acid bacteria lactis

Lactic acid bacteria are common contaminants of distillers fermentations. E. lactis may produce excessive amounts of volatile acids. Some species convert glycerol to fdpropionaldehyde which may break down to acrolein during distillation, producing an acrid odor. 

The inability to obtain complete protein sequence analysis of purified bacteriocins has been reason to suspect the presence of N-blocked peptide sequences (34) or lantibiotic residues (14). Recently, Piard et al. (14) have shown from partial sequencing and composition analysis that lacticin 481, a broad spectrum bacteriocin produced by L. lactis 481, also contains lanthionine residues. The early widespread interest in nisin and nisin-producing strains had given the impression that lantibiotics may be characteristic of bacteriocins of lactic acid bacteria. However, recent studies with other LAB bacteriocins suggest that simple peptide bacteriocins may prevail among the LAB. 

Fruity flavor in Cheddar cheese is also associated with high levels of ethyl butyrate and ethyl hexanoate (Bills et al. 1965). However, this defect is usually caused by esterase activity from lactic acid bacteria, especially S. lactis and S. lactis subsp. diacetylactis (Vedamuthu et al. 1966). Fruity-flavored cheeses tend to have abnormally high levels of ethanol, which is available for esterification (Bills et al. 1965). Streptococcal esterase activity in cheese is affected by the level of glutathione, which suggests a dependence on free sulfhydral groups for activity (Harper et al. 1980). 

Galesloot, T. E. 1956. Lactic acid bacteria which destroy the antibioticum (nisin) of S. lactis. Ned. Melk. Zuiveltijdschr. 10, 143-154. (Dutch)... 

Mellerick, D. and Cogan, T. M. 1981. Induction of some enzymes of citrate metabolism in Leuconostoc lactis and other heterofermentative lactic acid bacteria. J. Dairy Res. 48, 497-502. 

In the current industrial process, nisin is manufactured by fermentation of L. lactis subsp. lactis in a milk-based medium. Biosynthesis of nisin is coupled with the growth of lactic acid bacteria and the production of a significant amount of lactic acid (7). Lactic acid is an important chemical for food processing. It can also be used as a raw material in the production of the biodegradable polymer poly(lactic) acid (12). Unfortunately, lactic acid is not recovered in the current nisin process. 

Kleerebezemab, M., Hols, P., and Hugenholtz, J. 2000. Lactic acid bacteria as a cell factory rerouting of carbon metabolism in Lactococcus lactis by metabolic engineering. Enz. Microbial Technol., 26, 840-848. 

Nisin is an antibacterial polypeptide produced by some strains of Lactococcus lactis. Nisin-like substances are widely produced by lactic acid bacteria. These inhibitory substances are known as bacteriocins. Nisin has been called an antibiotic, but this term is avoided because nisin is not used for therapeutic purposes in humans or animals. Nisin-producing organisms occur naturally in milk. Nisin can be used as a processing aid against gram-positive organisms. Because its effectiveness decreases as the bacterial load increases, it is unlikely to be used to cover up unhygienic practices. 

Lactococcus lactis is the best characterized species among the lactic acid bacteria (Kim, Jeong, and Lee, 2007). 

The growth of microorganisms may have an important effect on the flavour of food. An example is the lactic acid bacteria Lactococcus lactis, which produce mainly lactate providing a characteristic acidic flavour and contributing to the preservation of fermented food. In an innovative approach, in situ 13C NMR was used to investigate glycolysis by an L. lactis strain deficient in lactate dehydrogenase.272... 

Most polysaccharides used today are of plant origin. However, also bacteria produce polysaccharides. Especially extracellular polysaccharides (eps s) produced by lactic acid bacteria may find application in foods. Lactic acid bacteria are food-grade organisms and the eps s produced offer a wide variety of structures. The presence of eps is considered to contribute greatly to texture and structure of fermented milk products. An exopolysaccharide produced by Lactococcus lactis ssp. cremoris B40 was chosen as a subject of study. The eps was a gift from the Dutch Institute of Dairy Research (NIZO), Ede, the Netherlands. The eps had no gelling properties, could not be precipitated in plates by ethanol or cetylpyridinium chloride and did not show interaction with Congo red. 

FemSndez, M., Linares, D. M., Alvarez, M. A. (2004). Sequencing of the tyrosine decarboxylase cluster of Lactococcus lactis IPLA 655 and the development of a PCR method for detecting t5trosine decarboxylating lactic acid bacteria. Journal of Food Protection, 67, 2521-2529. 

Settanni, L., Massitti, O., Van Sinderen, D., Corsetti, A. (2005). In situ activity of a bacterio-cin-producing Lactococcus lactis strain. Influence on the interactions between lactic acid bacteria during sourdough fermentation. Journal of Applied Microbiology, 99, 670-681. 

Lactobacillus and Propionibacterium strains were evaluated by El-Nezami et al. (2002) regarding their ability to remove seven Fusarium toxins (trichothecenes) from solution. Results showed that L. rhamnosus GG and Propionibacterium freudenrei-chii spp. shermanii JS were able to bind 18-93% of the deoxynivalenol, diacetoxy-scirpenol, and fusarenon in solution, while L. rhamnosus LC-705 removed 10-64% of deoxynivalenol and diacetoxyscirpenol from liquid medium. When comparing the ability of lactic and propionic bacteria to remove toxin from solution, Niderkom, Boudra, and Morgavi (2006) found that deoxynivalenol and fumonisin removal was strain specific, and that in general propionic acid bacteria was less efficient than lactic acid bacteria. The best results were achieved with L. rhamnosus for ranoval of deoxynivalenol (55%), Leuconostoc mesenteroides for fumonisin Bi (about 82%), and L. lactis for fumonisin B2 (100%) (Niderkom et al., 2006). 

Produced by Lactococcus lactis food-grade natural antibiotic produced by lactic acid bacteria see Chapter 15. 

De Vuyst, L., Vandamme, E.J., 1994. Nisin, a lantihiotic produced by Lactococcus lactis suhsp. lactis properties, biosynthesis, fermentation and apphcations. In Bacteriocins of Lactic Acid Bacteria. Springer, pp. 151—221. 

Lactic acid bacteria synthesise a range of different polysaccharides, defined by their location in the cell. Some are located intracellularly and are used as energy or carbon sources others are cell wall components and some are located outside the cell wall. The latter are called extracellular polysaccharides (EPs) and are either associated with the cell wall as a slime capsule, or secreted into the environment. Many lactic acid bacteria such as Lactobacillus delbrueckii subsp. bulgaricus, Streptococcus thermo-philus and Lactococcus lactis subsp. cremoris produce EPs. 

Nisin (C143H230N42O37S7) is an antibiotic produced by Streptococcus lactis and is effective against the Gram-positive bacteria, especially the lactic acid bacteria. It is used in processed cheese and some canned foods where permitted (see section 6.7). 

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