Chinese hamster ovary (CHO) cells are one of the most commonly utilized expression systems for the production of biopharmaceutical products, principally because they have been well-characterized and there is a history of regulatory approval for recombinant proteins produced from these cells. Employing recombinant DNA technologies, CHO cells used in the biopharmaceutical industry are genetically manipulated enabling the production of proteins of interest. These cells are classed as genetically modified microorganisms (GMM). Current European Union (EU) legislation requires the biopharmaceutical industry to comply with regulations governing the contained use of GMM (Council Directive 98/81/EC, amending Direc-tive 90/219/EEC).1 In Ireland, the Environmental Protection Agency (EPA) is the competent authority responsible for the implementation of Directive 98/81/EC, transposed into Irish law by the Genetically Modified Organisms (contained use) Regulations, S.I. No. 73 of 2001. The directive covers any activity involving the genetic manipulation, culturing, usage, storage, and destruction of GMM. Under the directive, there is a mandatory requirement for waste-containing Class 2 to 4 GMM to be inactivated prior to discharge. Inactivation of Class 1 GMM is optional but may be stipulated in certain circumstances by the competent authority. Inactivation refers to the destruction of GMM, ensuring that subsequent contact between the GMM and the general public or environment is limited, thereby providing an enhanced level of protection.
GMM inactivation may be achieved by thermal or chemical treatment. Heat treatment is the most common method of inactivating liquid effluent and may involve autoclave decontamination or the use of heat inactivation or "kill" systems.2,3 Chemical treatment involves the addition of a bactericidal agent capable of inactivating the GMM and generally consists of the manual addition of chemicals such as chlorine, caustic solutions, or iodophor compounds.
CHEMICAL INACTIVATION STRATEGY
NaOCl is a broad-spectrum antimicrobial agent.5 However, its corrosive nature renders it unsuitable for in situ cell inactivation in stainless-steel stirred tank reactors. NaOH, as a disinfectant and cleaning agent, is compatible with stainless-steel tanks, is effective in dissolving proteins and denaturing nucleic acids, and is widely used in the pharmaceutical industry for cleaning, sanitizing, and system storage.5 As NaOCl and NaOH are sensitive to the chemical environments in which they are used and their activity may be modulated by the presence of large amounts of protein, validation of the inactivation procedures is required to confirm that inactivation is effective and reproducible within normal working conditions at the site.