Pediococcus damnosus
Classification
Description and Significance
Pedicocci are found in fruit, fermented foods and plant material. Pediococcus damnosus is gram-positive bacteria that are obligate anaerobes metabolizing the sugars among carbohydrates resulting with fermentation. Its morphology displays short chains of cocci cells (0.3-0.6 mm in diameter). Round colonies express an off white/cream pigmentation while spores, capsules and motility are all absent. Figure 1-1 is a malolactic fermentation bacterium that shows Pediococcus morphology.
Growth
Among food and plant material, glucose, sucrose and galactose are metabolized while some strains of the bacteria will ferment maltose and sucrose in addition. This particular species is facultative allowing the metabolic processes to undergo with or without oxygen. With glucose, sucrose and galactose being primary targets for this microbe, it is one of the most common and well-known spoilers of wines, ciders, beers and juices. Other common microbes responsible for beer and wine spoilage include Acetobacter, Gluconobacter, Megasphaera cerevisiae, Saccharomyces diastaticus and Candida valida. Faster detection of Pediococcus damnosus and other contaminating microbes will help prevent the spoilage of produced beverages and stop the unnecessary loss of countless dollars for their companies.
Lactic Acid Bacteria
Bacteria found among food spoilage and food-borne pathogens are abundant. Lactic acid bacteria (LAB) are found among Pediococcus damnosus. Experiments have proven that this bacterium is associated with both food and beverage spoilage. More so, Lactobacillus phage B1 genome has 97 percent identity with Pediococcus damnosus; ensuring that it affects spoilage just as lactic acid bacteria does (Marco, 2012).
Lactic Acid Bacteria In Wine
======Lactic acid bacteria play an important role for wine quality. A species-specific multiplex PCR system was used to undergo an experiment to detect the presence of LAB species in Pediococcus damnosus. DNA extraction, multiplex PCR and the analysis of results prove that LAB is present in this microbe. The strain shows extreme resistance to ethanol and other influences so they are likely to appear during or after malolactic fermentation (Petri, 2012).
Companies have benefited from researchers developing a rapid method that can be used for detection, quantification, and identification of this microorganism. GC-MS and other slow cultivation and microscopy techniques are being replaced by analytical methods and test kits that that only take 12 hours to complete (Brodmann, 2011). These new methods look for certain DNA sequences in order to determine the presence of contamination, and if so, how much and which species.
Some strains of microorganisms are capable of surviving and multiplying rapidly even after the fermentation and sulfating processes of wine production. There are strict microbiological regulations and qualifications that beverages must pass before being sold, so contamination is a costly problem. Figure 2-2 shows the start of fermentation in different flavors of wine. Certain strains of Pediococcus damnosus can synthesize β-D-glucan, a glucose homopolymer that changes the viscosity of wine to be thicker than oil (Delaherche, 2004). These microorganisms used to be detected and quantified by selective counting on MRS plates, where the colony-growth step took seven days. Researchers have now developed a more time-efficient method (taking one day) using real-time quantitative PCR as a new technique that can be used for routine screening (Delaherche, 2004).======
Laboratory Studies
======Pediococcus damnosus produces exopolysaccharides that change the viscosity of and ruin products. Primers PF5 and PF6 have been analyzed via PCR, along with new primers PF1 and PF8 that target the dps gene (putatative glucan synthase gene). This gene was found vastly among isolated strains of both Pediococcus damnosus and Oenococcus oeni (Walling, 2005). In order to ascertain that the cells were indeed producing the wine-spoiling glucan, an aggregation test (binding test) was performed with Streptococcus pneumoniae type 37-specific antibodies. Agglutination proved that there is a direct relation between gene dps and glucan production (Walling, 2005). This shows that gene dps could be the cause of exopolysaccharide production not only in Pediococcus damnosus, but in Oenococcus oeni as well.
The microbe is further studied with different controls to determine resistance and sensitivities. Pediocin PD-1 is one, of many studied, bactericidal antimicrobial peptides. Pediococcus damnosus produces pediocin PD-1 and so researchers find this microbe to be timely. A gel electrophoresis experiment was used to detect pediocin PD-1 to be a molecular mass of 35 kDa. Researchers continued to undergo experiments with pediocin PD-1 determining the isoelectric point and antimicrobial activity. Results from their tests revealed that pediocin PD-1 is also resistant to specific treatments (Green, 1997).======
