Live Dirt: - Bacteria and Fungi
Typically, this column focuses on sources, detection, and avoidance or elimination of contamination, regardless of viable status. However, bacterial and fungal contamination are perennial concerns with variable, often unpredictable negative impact on processes and products.
viable contamination issues in pharmaceuticals, biotechnology, and biomedical devices is legendary; those involved face an ever-increasing blizzard of specifications and standards, including testing and monitoring requirements. Perhaps less obvious is the potential for fungal/bacterial contamination of processes and product during seemingly less critical production of product or support material (equipment, fixturing, and disposables).
Viable contaminants impact their environment through multiplication and production of by-products. Bacteria are microscopic single-celled animals. Fungi, including yeasts, rusts, molds, and mildew, are primitive plants with no chlorophyll. They are also a bit like animals in that they require a carbon-based (organic) source of nutrition.
Both bacteria and fungi are ubiquitous and adaptive in their environmental requirements. They are an important, often desirable, part of the ecosystem. Fungi are essential to the production process of cheese, bread, beer, and wine. An optimal level of desirable bacteria is necessary for appropriate functioning of the digestive system. Sometimes, the two occur together in a cooperative, synergistic relationship. They may compete in an antagonistic relationship. For example, some who take Penicillin, (a toxin produced by Penicillium mold) to quash a bacterial infection may become acutely and unpleasantly aware that it is a toxin which destroys beneficial intestinal bacteria.
Bacteria and fungi require warmth, a food source, and moisture to develop. They can multiply rapidly (picture ants at a picnic, crabgrass, pet rabbits, paperwork on your desk). Because their growth can be exponential and uncontrollable, we want to eliminate, or tightly control, both bacteria and fungi in industrial processes. Once they start to grow, they can compromise the product and the process; and decontamination is often difficult. One problem is that both bacteria and fungi can form spores, which are a bit like seeds remaining dormant or inactive under suboptimal conditions, only to begin multiplying when suitable sources of food, heat, and moisture become available.
To determine whether mold or bacteria can impact your industrial process, product, or environment, answer the following:
* Is the liquid or solid substrate a food source?
* Does the solid substrate have food (perhaps an organic contamination) on the surface?
In either case, viable contamination is a potential issue. If the product is biodegradable, it’s a food source and can be destroyed by bacteria and mold. This is a positive feature in hazardous waste management, but potential problems in manufacturing.)Biodegradable products are ubiquitous in production. Biodegradable plastics and elastomers which might be found in seals include Delrin®, polyurethane, and natural rubber. While PVC tubing is not biodegradable, polyethylene tubing can be a food source. Some filters are ceramic; far more are paper-based. Allow spores to settle on the part; add high humidity and elevated temperatures; and you have the potential for contamination.
Growth can also occur in industrial fluids. Mold has been detected in diesel fuel. Bacteria can contaminate cutting oils, (especially water-soluble oils) and grinding lubricants. In addition to organic sources, some inorganic materials act as supplements to boost the growth rate. For example, some bacteria grow more rapidly in environments which include iron, manganese, even aluminum. Process tanks and effluent lines can change from a clear fluid to a visibly darkened, often foul-smelling solution within the course of a few days. Aesthetic concerns aside, developing life-forms modify the industrial fluid both by their presence and by depletion of organic and perhaps key inorganic additives.
Growth can be prevented with appropriate additives. However, the selection and use of anti-bacterial or anti-fungal products is somewhat controversial in that the requirement to kill microbes must be balanced with worker and community safety concerns.