Manufacturing with Microbial Control in Mind (Part I)

By Beth Ann Browne, Jeff Van Komen and Jeffrey Domsic, Tony Rook and Cecilia McGough, The Dow Chemical Company; he Procter & Gamble Company; The Sherwin-Williams Company; Lanxess Corporation | April 3, 2017

Experts from a variety of industries review the five key components to keep bugs at bay.

Manufacturing with microbial control in mind is crucial for providing customers with high-quality consumer, household and industrial (CH&I) products that are safe and effective. CH&I products include, but are not limited to, household cleaners, hand dish soaps, laundry products and paint, all of which are primarily water-based with an ever-increasing composition of naturally-derived raw materials. These compositional features inherently create a situation in which CH&I products could be highly susceptible to microbial contamination, especially during the manufacturing process. Microorganisms proliferate in aqueous environments and can use the organic components in the formulations as their nutrient source.  In addition, naturally-derived raw materials can harbor microorganisms and become a source of microbial contamination in the final CH&I product. This article will outline the fundamental manufacturing principles to ensure that the final CH&I product remains uncompromised by microbial contamination.

Consequences of Contamination

Microbial contamination can have consequences that include significant changes in a CH&I product’s properties, including viscosity shift, pH drift, color change, foul odor and destruction of the product’s performance.1 The predominant concern with contamination of CH&I products is poor product stability and inadequate product performance, which can lead to recalls and ultimate disposal of nonconforming products. However, some consumer products have been recalled from the marketplace as a direct result of microbial contamination. Consumer products that contain high levels of microorganisms may contribute to adverse health-related issues, particularly in immunocompromised individuals and otherwise sensitive populations. 

The use of US EPA registered preservatives is often critical for controlling the growth of microorganisms in CH&I products.2 Although long-term preservatives can be used to help prevent product contamination during consumer use after manufacturing, it is important that CH&I products leave the manufacturing facility without elevated levels of spoilage microorganisms. If a CH&I product is heavily contaminated with bacteria and/or fungi during the manufacturing process, the preservative package can be completely consumed, leaving the product without preservative for the remainder of its lifecycle.

Beyond damage to the products themselves, microbial contamination can be detrimental to manufacturing facilities and processes. Within production facilities, microbial contamination can cause cross-contamination of other areas and materials such as raw materials and final products, corrosion of storage tanks and transfer lines, decreased production rate and interruption of facility operations. Another major concern with microbial contamination is the formation of biofilms, which are communities of microorganisms attached to surfaces and held together by a matrix of material referred to as extracellular polymeric substances (EPS).3 Biofilms can contain a single bacterial species or (more commonly) multiple species. Biofilms can plug heat exchangers and contaminate filters, transfer lines and nozzles during manufacturing. Biofilms present a complication because they often require a biocide treatment concentration of 10 to 1,000 times higher than the concentration needed for planktonic (or free floating) cells.4,5,6,7 In addition, biofilms are extremely difficult to remove from manufacturing processes with cleaning and sanitization procedures; however, proactive cleaning steps can preclude the need for extensive deep cleaning. 

The remainder of this article will outline the necessity of good housekeeping strategies along with the five key components for effective microbial control. 

Good Housekeeping Strategies

Proactive housekeeping practices partially decrease the need for reactionary cleaning and sanitization steps and positively influence downstream product quality. Good housekeeping is a long-term, continuous process,8 and the practices provide multiple benefits for safety of personnel and prevention of microbial contamination. Good housekeeping procedures should be documented in Standard Operating Procedures (SOPs) and included in personnel training. Employee hygiene is an important factor in good housekeeping, and it is recommended that employees wash their hands after eating and using the restroom to avoid potential cross-contamination of manufacturing equipment, raw materials and final products. Uniforms and/or dress codes are also part of employee hygiene. Beyond hygiene, SOPs can address other housekeeping concerns that can contribute to microbial contamination, such as pest control, air exchange, reducing clutter, cleaning schedule, proper handling of spills and eliminating stagnant water on the production floor. Good housekeeping is the foundation on which the five key components for effective microbial control are built.   

A Five Component System for Microbial Control

This article will focus on the importance of a holistic microbial control program with five key components, which include: 1. Facility and equipment design; 2. Cleaning; 3. Sanitization; 4. Monitoring and 5. documentation, as illustrated in Figure 1. 

Facilities and equipment should be designed to minimize possibilities for microbial contamination. Cleaning refers to the physical removal of items such as dirt, debris, standing water, and product residues from surfaces in the facility.  Without the cleaning step the effectiveness of the sanitization step is greatly reduced or completely ineffective. Sanitization refers to the process of decreasing the number of viable microorganisms to an acceptable level in all components in the manufacturing process.

Monitoring refers to routine evaluations of processes to determine the effectiveness of the system for microbial control. Documentation refers to both the existence of a written procedure to address microbial control as well as the recorded observations in the facility surrounding contamination events.       

Facility and Equipment Design

Facility and equipment design can cause significant challenges for industrial hygiene. Properly designed equipment will reduce the microbial risks from equipment, facilities and processes where products are manufactured. As CH&I products are not intended to be sterile, there is a risk for microbial contamination. Defining and applying fundamental principles for equipment and facility design can significantly reduce the risk of microbial contamination. 

It is recommended that any manufacturing process be built in a manner that minimizes the risk of microbial contamination for the product. However, many CH&I products will be produced on legacy manufacturing systems or in repurposed facilities where only minimal modifications are possible. In these instances, additional procedural or mitigation strategies are suggested. For example, increased frequency of cleaning and sanitization may be necessary. Also, system components that present the greatest microbial risk can be identified, and plans to reduce these risks should be developed into any site capital upgrade plans. Likewise, appropriate preventative maintenance will help to reduce risks within the manufacturing environment.

Within facilities, the equipment design should be based upon specific design standards that account for risks to the specific product type to be manufactured. It is recommended that a company develop specific minimum clean design standards. Some principles that can be incorporated into these standards are: material used for construction, material flow through the systems, and pump and valve designs. In addition, design elements should consider the potential to clean the systems in place, sanitize in place, and drain in place. These three fundamentals will enable minimal downtime and will reduce overall microbial risks to the manufacturing system. Specifically, proper drainage is imperative for systems as stagnant water creates risk of microbial contamination.

An integral part of facility and equipment design is to establish principles regarding effective change control management with appropriate microbiologist input. Changes to equipment may require new validations, specific design elements to reduce microbial risk, changes in environmental sampling locations and frequency, and cleaning and sanitization revisions based on equipment design changes.


Cleaning is the act of removing dirt, particles, or foreign materials from a surface.  It is essential that cleaning is performed prior to sanitization steps to ensure the greatest likelihood of microbial control.  For example, a layer of product left on the inside of a storage tank can prevent a sanitizer from coming into contact with the side of the tank.  As a result, microorganisms can remain between the residue and the wall of the tank.  Due to this risk, cleaning procedures and success criteria should be validated prior to production. Metrics for successful cleaning include: physical checks, suds free, physicochemical tests such as total organic carbon (TOC), and/or conductivity of the returned rinse water in comparison to the fresh rinse water, etc. 

Different methods can be employed for effective cleaning including physical/mechanical cleaning, such as scrubbing and flushing, as well as the use of chemical cleaning agents. Often these methods are used in combination. Desirable characteristics of cleaners include appropriate surface active properties, easily removable and material compatibilities. Failure to use compatible materials can result in costly damage to the equipment. As an example, pitting of metal will make the equipment more difficult to clean and can lead to premature failure and early replacement. 

If previously validated metrics have been met and the cleaning agent is adequately removed from the system, sanitization can be performed.


Equipment sanitization procedures are used subsequent to the aforementioned cleaning procedures to reduce bioburden to a (previously established) acceptable level in all components of the manufacturing system.  Sanitizing typically involves the use of heat or chemicals or a combination of both. While chemical sanitizers such as 70% alcohol and hypochlorite are effective, incompatibility is often an issue.  Therefore, a very efficient method of sanitization is typically moist heat (either water or steam). 

An accepted industry standard is total exposure to 80°C for 30 minutes; however, lower temperatures and/or shorter durations can be used. A sanitizer, like a cleaning agent, must be compatible with the material(s) which it contacts. Prior to implementing sanitization procedures, it is strongly recommended to validate the effectiveness of the sanitization process for variables such as concentration of active ingredient, contact time and use location through microbiological testing to determine the level of reduction in viable microorganisms. Preservatives are not sanitizers, should not be used as sanitizers, and are not replacements for sanitization. 

Microbial Monitoring

Microbial monitoring refers to evaluations conducted to determine if sufficient microbial control in the manufacturing facility exists. Effective monitoring involves a systematic approach, which considers the entire manufacturing process. Some sites in the manufacturing facility are more critical than others due to their susceptibility to microbial contamination. 

The exact specification to meet depends on the general classification of the manufactured product, the specific type of product, how it will be used, and if a specification currently exists, perhaps due to a downstream customer requirement. Not all product types have specific industry standards for microorganism limits. The CSPA Cleaning Product Division Microbiology Subcommittee has published some voluntary General Guidance and Method Guidance documents for household, industrial and institutional (HI&I) products and their raw materials.9,10,11  The Microbiological Quality of Household and Institutional Products General Guidelines (MGG 002.1 2014) suggest that manufacturers “evaluate the microbiological quality of their products and establish appropriate, rational and actionable limits based on the best technical considerations and in context of finished product uses and label directions.”10  Some considerations include chemical compositions, product history, formulation, raw materials and the manufacturing process. While CH&I products are not sterile, these guidelines suggest appropriate acceptance criteria.

Monitoring plans often include testing of raw materials, water including recycled water (if applicable), final products, reworked products and manufacturing equipment. Facilities may need to modify their procedures during certain times of the year due to seasonal spikes of contamination. These may include summer temperature spikes, seasons of slow moving inventory, spring and fall air quality issues and periods of system shutdown. Additionally, effective rodent, insect and bird control procedures are necessary. A facility’s geographic location impacts all of the aforementioned points.  Based on the results of initial self-inspection activities, the proposed monitoring program can be altered to best fit the needs of the individual facility.  


Documentation reinforces a regimented microbial control plan, which can include: manufacturing procedures; logs of housekeeping, cleaning, and sanitization activities performed; records of past microbial audits; batch records documenting specific lots of raw materials and microbial analysis of those lots; in-process samples and final product retain analyses; and past microbial remediation activities. With these records, periodic data analysis is possible to identify times of the year or situations that are problematic for microbial control, and proactive changes can be made to hygiene procedures, including sampling frequency and locations and/or preservative use. Documentation allows for the crucial activity of tracing back to determine where a problem may have originated and if necessary, provides key information to conduct an efficient and successful product recall.  In summary, documentation is important so that vital information is not lost over time or with personnel changes.    

Conclusion and Next Steps
Today’s CH&I products can be more susceptible to microbial contamination due to increased water content and naturally derived raw materials. A proactive approach is recommended, in order to minimize total bio-burden during the manufacturing process, maximize preservative longevity and product shelf life, avoid product recalls and maintain customer trust in your brand. This article introduced the five key components for manufacturing with microbial control in mind. In Part 2, which will be published in the May issue, the application of these principles will be described from end to end in manufacturing. 

  1. American Chemistry Council Biocides Panel. (2010). Benefits of Antimicrobial Pesticides in Public-Health and Industrial Uses.
  2. Shaw, D. A., Browne, B., Rook, T., Geis, P., & Ananth, V. (2014, May). Critical Elements of Household Product Preservation. Happi, 79-85.
  3. Costerton, J. W., Lewandowski, Z., Caldwell, D. E., Korber, D. R., & Lappin-Scott, H. M. (1995). Microbial Biofilms. Annual Reviews of Microbiology, 49, 711-745.
  4. Mah, T.-F. C., & O’Toole, G. A. (2001). Mechanisms of Biofilm Resistance to Antimicrobial Agents. Trends in Microbiology, 9(1), 34-39.
  5. Nickel, J.C. et al. (1985). Tobramycin resistance of Pseudomonas aeruginosa cells growing as a biofilm on urinary tract catheter. Antimicrob. Agents Chemother, 27, 619-624.
  6. Evans, R., & Holmes, C. (1987). Effect of vancomycin hydrochloride on Staphylococcus epidermidis biofilm associated with silicone elastomer. Antimicrob. Agents Chemother, 31, 889-894.
  7. Gristina, A.G. et al. (1987). Adhesive colonization of biomaterials and antibiotic resistance. Biomaterials, 8, 423-426.
  8. Trotto, S. (2015, July 1). Safety+Health The Official Magazine of the NSC Congress & Expo. Retrieved from 11 Tips for Effective Workplace Housekeeping: http://www.safetyandhealthmagazine.com/articles/print/12470-tips-for -effective-workplace-housekeeping
  9. CSPA Cleaning Products Division Microbiology Subcommittee. (2014). Microbiological Examination of Household and Institutional Products: Method Guideline for Microbial Enumeration Tests MMG 001.1 2014.
  10. CSPA Cleaning Products Division Microbiology Subcommittee. (2014). Microbiological Quality of Household and Institutional Products General Guidelines MGG 002.1 2014.
  11. CSPA Cleaning Products Division Microbiology Subcommittee. (2014). Microbiological Quality of Raw Material General Guidelines MGG 003.1 2014.

CSPA Microbiology Preservative Subcommittee
The CSPA Microbiology Preservative Subcommittee (MPS) is committed to microbiological quality. To support these goals, a Microbial Control Stewardship Task Force communicates effective preservation strategies.  Website: www.cspa.org