Enzyme Technology
Safety and regulatory aspects of enzyme use
Only very few enzymes present
hazards, because of their catalytic activity, to those handling them in normal
circumstances but there are several areas of potential hazard arising from their
chemical nature and source. These are allergenicity, activity-related toxicity,
residual microbiological activity, and chemical toxicity.
All enzymes, being
proteins, are potential allergens and have especially potent effects if inhaled
as a dust. Once an individual has developed an immune response as a result of
inhalation or skin contact with the enzyme, re-exposure produces increasingly
severe responses becoming dangerous or even fatal. Because of this, dry enzyme
preparations have been replaced to a large extent by liquid preparations,
sometimes deliberately made viscous to lower the likelihood of aerosol formation
during handling. Where dry preparations must be used, as in the formulation of
many enzyme detergents, allergenic responses by factory workers are a very
significant problem particularly when fine-dusting powders are employed. Workers
in such environments are usually screened for allergies and respiratory
problems. The problem has been largely overcome by encapsulating and granulating
dry enzyme preparations, a procedure that has been applied most successfully to
the proteases and other enzymes used in detergents. Enzyme producers and users
recognise that allergenicity will always be a potential problem and provide
safety information concerning the handling of enzyme preparations. They stress
that dust in the air should be avoided so weighing and manipulation of dry
powders should be carried out in closed systems. Any spilt enzyme powder should
be removed immediately, after first moistening it with water. Any waste enzyme
powder should be dissolved in water before disposal into the sewage system.
Enzyme on the skin or inhaled should be washed with plenty of water. Liquid
preparations are inherently safer but it is important that any spilt enzyme is
not allowed to dry as dust formation can then occur. The formation of aerosols (e.g., by poor operating procedures in centrifugation) must be avoided as these are at
least as harmful as powders.
Activity-related toxicity is much rarer but it must
be remembered that proteases are potentially dangerous, particularly in
concentrated forms and especially if inhaled. No enzyme has been found to be
toxic, mutagenic or carcinogenic by itself as might be expected from its
proteinaceous structure. However, enzyme preparations cannot be regarded as
completely safe as such dangerous materials may be present as contaminants,
derived from the enzyme source or produced during its processing or storage.
The
organisms used in the production of enzymes may themselves be sources of
hazardous materials and have been the chief focus of attention by the regulatory
authorities. In the USA, enzymes must be Generally Regarded As
Safe (GRAS) by the FDA (Food and Drug Administration) in
order to be used as a food ingredient. Such enzymes include a-amylase, b-amylase,
bromelain, catalase, cellulase, ficin, a-galactosidase, glucoamylase, glucose isomerase, glucose oxidase,
invertase, lactase, lipase, papain, pectinase, pepsin, rennet and trypsin. In
the UK, the Food Additives and Contaminants Committee (FACC) of the Ministry of
Agriculture, Fisheries and Food classified enzymes into five classes on the
basis of their safety for presence in the foods and use in their
manufacture.
Group A. Substances that the available evidence
suggests are acceptable for use in food.
Group B. Substances
that on the available evidence may be regarded as provisionally acceptable for
use in food but about which further information must be made available within a
specified time for review.
Group C. Substances for which the
available evidence suggests toxicity and which ought not to be permitted for use
in food until adequate evidence of their safety has been provided to establish
their acceptability.
Group D. Substances for which the
available information indicates definite or probable toxicity and which ought
not to be permitted for use in food.
Group E. Substances for
which inadequate or no toxicological data are available and for which it is not
possible to express an opinion as to their acceptability for use in food.
This
classification takes into account the potential chemical toxicity from microbial
secondary metabolites such as mycotoxins and aflotoxins. The growing body of
knowledge on the long-term effects of exposure to these toxins is one of the
major reasons for the tightening of legislative controls.
The enzymes that fall
into group A are exclusively plant and animal enzymes such as papain, catalase,
lipase, rennet and various other proteases. Group B contains a very wide range
of enzymes from microbial sources, many of which have been used in food or food
processing for many hundreds of years. The Association of Microbial Food Enzyme
Producers (AMFEP) has suggested subdivisions of the FACC's group B into:
Class ain8 microorganisms that have traditionally been
used in food or in food processing, including Bacillus subtilis,
Aspergillus niger, Aspergillus
oryzae, Rhizopus oryzae,
Saccharomyces cerevisiae,
Kluyveromyces fragilis,
Kluyveromyces lactis and Mucor
javanicus.
Class bin8 microorganisms that
are accepted as harmless contaminants present in food, including
Bacillus stearothermophilus,
Bacillus licheniformis, Bacillus
coagulans, and Klebsiella
in8aerogenes.
Class cin8 microorganisms
that are not included in Classes b and c, including Mucor
miehei, Streptomyces albus,
Trichoderma reesei, Actinoplanes
missouriensis, and Penicillium
emersonii.
It was proposed that Class a should not be subjected
to testing and that Classes b and c should be subjected to the following tests:
- acute oral toxicity in mice and rats,
- subacute oral toxicity for 4 weeks
in rats,
- oral toxicity for 3 months in rats, and
-
in vitro mutagenicity.
In addition Class c should be tested for
microorganism pathogenicity and, under exceptional circumstances,
in vivo mutagenicity, teratogenicity, and carcinogenicity.
The
cost of the various tests needed to satisfy the legal requirements are very
significant and must be considered during the determination of process costs.
Plainly the introduction of an enzyme from a totally new source will be a very
expensive matter. It may prove more satisfactory to clone such an enzyme into
one of AMFEP's Class a organisms but this will first require new legislation to
regulate the use of cloned microbes in foodstuffs. Some of the safety problems
associated with the use of free enzymes may be overcome by using immobilised
enzymes (see Chapter 3). This is an extremely safe technique, so long as the
materials used are acceptable and neither they, nor the immobilised enzymes,
leak into the product stream.
The production of enzymes is subject, in the UK, to
the Health and Safety at Work Act 1974, to ensure the health and safety of
employees. Good manufacturing practice is employed and controls ensure that
enzyme production is performed by a pure culture of the producing
microbes.
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This page was established in 2004 and last updated by Martin
Chaplin on
6 August, 2014
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