Bacteriophages and Their Current Significance in Dairy Industry - Term Paper Example

Running head: Dairy Science Bacteriophages and Their Current Significance in Dairy Industry Insert Insert Grade Insert 21 May 2012 Introduction Phages can have lactococci, sperm, or isometric shaped heads protein in nature. Phages attach themselves to bacterial cells using their tails at specific sites where they inject their DNA and start replicating. Phages attack bacteria using various ways, which can include lytic relationship where the bacteria phage commandeers the bacteria cell mechanism and releases new phages. In lysogenic relationship, the bacteria phage integrates with the bacteria cell becoming a prophage where it replicates without destroying the host bacterial cell. Partial infection of bacterial cells results in pseudolysogenic relationships. Bacterialphages are viruses that destroy bacteria and occur widely in the environment (Breitbart and Rohwer 278) and food products (European Food Safety Authority 4). Bacterialphages infect specific bacterium and transmit their DNA into the bacteria’s cell and effectively hinders the ability of the bacterium to survive and reproduce thus reducing the number of bacteria in a specific location (European Food Safety Authority 4). Bacteriaphage contamination remains a considerable culprit of low quality products in the dairy sector, and they thrive even under strict cleaning and disinfection regimens, necessitating use of combined strategies to minimize their undesired effects. Majority of raw milk contains all classes of bacterialphages with some LAB phages being heat resistant ensuring that bacterialphages continue to be of importance in any dairy plant (McGrath et al. 451). Effective destruction of all phages requires using high temperature time combinations, which render milk unsuitable to processing some dairy products especially cheese. Phage contamination in milk can arise from raw ingredients used in the dairy industry particularly during fermentation as lactic acid bacteria naturally present in milk may be a source of phages (Garneau and Moineau 2). Recycled and reprocessed ingredients during fermentation may add phages to the dairy product in low concentration, which would replicate causing product problems (Chopin 139). This may be eliminated by effectively heat treating any reprocessed ingredients starter cultures before use. Temperate phages can integrate into the bacterial chromosome resulting in lysogens, which may start lytic cycles during fermentation leading to hindered fermentation (Lunde et al. 721). The adaptive nature of phages may result in serious processing problems if a viable host is available as they would replicate very rapidly causing low quality products and low productivity (Bron and Kleerebezem 85). Contaminated dairy plant surfaces and air may cause phage contamination as some phages are airborne. This is increasingly possible because of liquid and milk splashes, which make the phages airborne (Moineau and Lévesque 291). Use in the Dairy Industry The use of bacterialphages as bio-control agents in the food industry heralds a new front; where the negative effects of chemical and physical means of controlling harmful bacteria can be avoided. Their use is limited by the possibility of the target bacteria developing resistance to phages, which can be a constant source of food contamination during processing (European Food Safety Authority 9). This can, however, be controlled and minimized through avoidance of recycling of bacteriophages and using different strains of bacteriophages in successful treatments as they have the capability to counter the resistance mechanism developed by bacteria through adaption mechanisms (European Food Safety Authority 9). Only the most virulent bacteriaphages that have a wide host range should be used as bio-control agents in the food industry as most exhibits very limited host ranges, which can render them inefficient unless strategically used (European Food Safety Authority 9). Various treatments may be used with passive treatment involving the use of bactriophages in large quantities sufficient in infecting all target bacteria and destroying them quickly (European Food Safety Authority 12). Small doses of the bacteriaphages may also be utilized with the primary objective of allowing them to replicate in the target bacterial eliminating them in the process (European Food Safety Authority 12). Their effective use should be based on proved efficiency against specific pathogenic bacteria whose characteristics are known. Improper use can result in target bacteria developing resistance, which can lead to higher costs in their control. Advantages of bacterialphages Phages are strain specific hence effective in destroying targeted bacteria. Their successful action is determined by their concentration and their proximity to the target bacteria hence should be used in favorable environments. Their use ensures beneficial bacteria are not affected during food processing, which is better compared to antibiotics that can wipe out entire bacterial populations regardless of their use. Bacteria phages may hold the key to the effective use of prebiotics and probiotics in the dairy sector (Bogosian 665); as they can selectively ensure that only the required microbes are present in the milk products by eliminating competing bacteria. Being natural and abundant in nature, they can be harnessed and used on a wide variety of unwanted bacteria in the food sector offering a cheap, safe, and better way of providing quality dairy products. Biofilm Treatment Insufficient cleaning and disinfection of dairy equipment leads to the development of biofilms, which are characterized by bacterial extracellular polymeric substances and milk sediments (Simo˜es et al. 573). These bacterial colonies are hard to destroy due to the complex structures they form and may lead to equipment degradation due to their inherent biological and chemical reactions, which may catalyze significant corrosion in pipes and tanks (Simo˜es et al. 573). These colonies may also hinder effective heat treatments due to the formation of plaques inside heat exchangers; contributing to energy losses and poor quality products prone to spoilage. Biofilms are notable because they are responsible for the constant and consistent spread of food borne diseases caused by listeria monocytogenes, yersinia enterocolitica, campylobacter jejuni, salmonella spp, staphylococcus spp, and Escherichia coli 0157:h7 (Lapidot 233). Biofilms offer these pathogenic microorganism suitable environments where they can replicate and produce toxins because of availability of a constant supply of nutrients and water. Bacteriophages can be successfully used in controlling biofilms in the dairy sector with the advantage of being specific, non toxic and natural; eliminating the need of harsh disinfectants that reduce the lifespan of dairy equipments (Lapidot 579). They are effective in degrading a wide range of biofilms and offer synergistic effect with alkaline disinfectants in the control of E.coli 0157:H7 biofilms formed on stainless steel, which can be of significant importance to the dairy industry all over the world (Lapidot 579). Control of Milk Microbial Pathogens Most milk pathogens cause severe diseases and are responsible for food outbreaks all over the world. Bacteriaphages can be used to eliminate their presence in food products guaranteeing safer dairy products for customers. Staphylococcal phages Staphylococcus aureus is resistant to most antibiotics and is a majorleading cause of bovine mastitis and milk contamination (Suárez et al. 3019). Staphylococcal phages are temperate and effective in the control of growth, replication, and development of staphylococcal strains that are responsible for mastitis and milk contamination (Suárez et al. 3026). They are effective in preventing the spoilage and quality deterioration of milk products due to temperature fluctuations during milk processing and storage (Suárez et al. 3026). Majority of dairy milk products require cold chain handling, and this can be economically beneficial because of elimination of losses arising from products spoilage and quality downgrading occasioned by temperature fluctuations due to mishandling, carelessness, and power failures. Listeria Monocytogenes Listeria phage p100 is used for the control of l.monocytogenes in soft cheese. Listera monocytogenes survives in a wide range of environmental conditions and is pivotal in raw and processed milk and dairy products (McGrath et al 453). Bacteriaphage use to eliminate these pathogens is a significant breakthrough in the dairy sector, which will reduce deadly epidemics from listeria monocytogenes especially present in cheese. Salmonella enteritidis SJ2 phage is effective against salmonella enteitidis in cheese manufacture. The bacteria phage is successful in complete destruction of s, enteridis and is active even after significant periods of cheese storage (McGrath et al. 453). Disadvantages Bacterialphages can infect fermentation bacteria including streptococcus, lactobacillus and lactococcus generas (Sturino and Klaenhammer 335) posing serious economic risks to dairy plants specializing in fermentation products. This is very important as bacterialphages appear in diverse environments making them an ever present risk to the dairy producer. Bacteriaphage infections can utterly destroy starter cultures used in fermentation leading to fermentation failures and huge losses as the milk is destroyed and cannot be reprocessed due to partial acidity (McGrath et al. 451). They disrupt production programs and schedules because of slow fermentation caused by partial destruction of the starter cultures leading quality inconsistencies of final products, which can be disastrous to established dairy brands (McGrath et al. 451). Milk products infected with bacterialphages lack proper development of flavor, aroma, and consistency qualities that cannot be improved once developed. Milk fermentation is severely limited by the presence of more than the critical thresh hold of 104 plaque forming units (PFU/ML); with more than 105-106 (PFU/ML) leading to complete failure of the fermentation process (Moineau and Lévesque 288). Bacterialphages are characterized by rapid replication and spread and they require adequate and effective control procedures if losses are to be avoided during processing. Control of Bacterialphages in the Dairy Sector Sanitation Effective phage control programs require the knowledge of the sources and risks of phage contamination in the processing chain. These programs must integrate factory design, efficient and effective cleaning, and disinfection of all production equipments. To reduce airborne phage contamination and spread, air filters should be properly installed and maintained. Effective and efficient cleaning agents are beneficial in control of phages in the dairy sector. Paracetic acid and hypochrolic acids are highly effective against LAB phages, which are heat resistant (Ebrecht et al. 515). The use of chemicals in the control of phages is limited by their corrosive effect and the possibility of chemical residues remaining in the production equipments. Ingredient Treatment All ingredients used in the dairy industry must be effectively sanitized to reduce the viable bacterialphages. Raw milk should be pasteurized at all times to reduce susceptible phage presence (Atamer 410). Starter Culture Selection and Use Starter cultures strains should be carefully selected to avoid phage susceptible cultures. Different strains of starter culture should be used together to minimize possible phage infections that would lead to slow fermentation or fermentation failures (Moineau and Lévesque 291). Starter Culture Preparation All bacterial starter cultures should be prepared preferably in isolated and positively pressurized rooms to prevent airborne contamination from the rest of the factory Starter Rotation To reduce the replication of specific phages in fermentation programs, rotation of starter culture should be observed with strict monitoring to detect any incidences of phage contamination and effective changes made to limit its spread (Moineau and Lévesque 291). Phage Inhibiting Media Phage inhibiting media is high in phosphates, low in calcium, and is especially important in starter preparations together with starter culture encapsulation as they limit the risk of phage attacks. Conclusion The primary objective of cleaning and disinfection regimens in any dairy fermentation plant is the control and elimination of any undesired microbial activity. This is achieved at several levels, but the dynamic and wide presence of bacterial phages in nature and consequently in dairy processing plants makes this impossible. Increased resistance of microorganisms to convectional cleaning processes requires integrated cleaning processes and use of new technologies to eliminate them. Unwanted bacterial phages should be controlled by incorporating effective plant designs, efficient air cleaning processes and effective cleaning and disinfection of equipment. This should be reinforced with efficient monitoring and detection procedures, which should include classification and characterization of these unwanted phages to enable effective control programs. Fermentation areas should be isolated from the rest of the dairy plant, especially in cheese manufacture sections where milk phage contamination milk is most likely during ripening and setting. Air aerosols produced during whey processing are potential phage contaminants. This is because they carry phage particles and these areas should be physically isolated from fermentation sections. Some phages can be used as bio-control agents in the dairy industry and are effective against known pathogenic microorganisms and this should be exploited to control the occurrence of food borne outbreaks, occasioned by them. Extensive and thorough research should be done to develop effective phage mixtures that can be able to act against a wide variety of pathogens. They should especially be used in the fermentation industry where they can help avoid huge financial losses occasioned by cold chain altercations that lead to dairy product spoilage. Works Cited Atamer, Zeynep et al. “Influence of the Suspension Media on the Thermal Treatment of Mesophilic Lactococcal Bacteriophages.” Int Dairy J, 20 (2010): 408-414. Print. Bogosian, Gregg. Control of Phage in Commercial Microbiology and Fermentation Facilities. 2nd Edition. New York: Oxford University Press, 1997. Print. 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Simo˜es, Manuel et al. “A Review of Current and Emergent Biofilm Control Strategies.” LWT - Food Science and Technology 43 (2010): 573–583. Print. Sturino, Joseph, and Klaenhammer Todd. “Bacteriophage Defense Systems and Strategies for Lactic Acid Bacteria.” Adv. Appl. Microbiol,56 (2004): 331-378. Print. Suárez, Evaristo et al. “Prevalence of Bacteriophages Infecting Staphylococcus Aureus in Dairy Samples and Their Potential as Biocontrol Agents.” J. Dairy Sci., 92 (2009): 3019–3026. Print. Read More