GLUCOSE ISOMERASE (Streptomyces violaceoniger)


         This enzyme preparation has not previously been reviewed by the
    Joint FAO/WHO Expert Committee on Food Additives.

         The enzyme preparation consists of whole cells of
    S. violaceoniger plus filter acids. The strain is reference number
    CBS 409-37 (Centraal Bureau voor Schimmelcultures). The organism is
    grown in a medium containing corn steep liquor, carbohydrate material
    containing xylose (corn cob), MgSO4 (1 g/l) and CoCl2 (0.01 g/l).
    The mycelial mass plus filtration acid (Fuller's earth) is separated
    from the fermentation mixture or a rotary vacuum filter, and flash

         The following streptomyces species are thought to be identical
    to S. violaceoniger: antimycoticus, chitaensis, endus,
    hygroscopicus jenssen, naganishu, nigrescens, noboritaensis,
    platensis, rutgersensis, tubercidicus, vastatus.

         Although many forms of S. violaceoniger produce antibiotics
    under certain conditions, no antibiotic was detected in concentrated
    mycelia or the incubation medium of S. violaceoniger CBS 409-73
    produced under industrial conditions. The level of sensitivity was
    equivalent to 2-5 µg/ml of neomycin.

         In use, the enzyme is added to glucose syrup in a concentration
    of 8 g/l, and is recovered by filtration.



    Acute toxicity and pathogenicity

         A culture of S. violaceoniger CBS 409-73 was prepared in broth
    (5% dextrose). The filtrate was injected intravenously into 10 mice in
    a dose of 0.2 ml per mouse. The culture suspension was injected
    intraperitoneally into 10 mice in a dose of 0.5 ml per mouse. The
    corresponding control mice were given non-inoculated medium. No
    mortality or behavioural abnormalities occurred over a 2-week period.

    Short-term studies


         Six groups each containing 10 male and 10 female Sprague-Dawley
    rats were assigned to the following treatments: I, normal feed and
    water; II, normal feed and 13.5% invert syrup (10% invert sugar in

    water); III, feed containing 5% used S. violaceoniger (lysed) and
    13.5% invert syrup prepared with S. violaceoniger and unrefined; IV,
    normal feed plus 13.5% invert syrup prepared with S. violaceoniger
    and unrefined; V, feed containing 5% fresh S. violaceoniger (lysed)
    plus water; VI, feed containing 5% used S. violaceoniger (lysed)
    plus water. The protocol may be summarized thus:


                             I      II     III      IV       V      VI

    Feed                     X      X               X

    + used S.v. (5%)                       X                        X

    + fresh S.v. (5%)                                        X

    Water                    X                               X      X

    + invert syrup                  X

    + S.v. invert syrup                    X        X

         Body weight and consumption of feed and water was recorded each
    week. The feeding trial continued for 4 weeks, then haematology, blood
    biochemistry, urine analysis, organ weight and histological
    examinations were made. Food consumption was below control values in
    rats drinking invert sugar solutions (Groups I, III and IV), in whom
    sugar intake exceeded 20 g/kg daily; these rats were hyperglycaemic.
    Weight gain was normal in all groups. There were no significant
    deviations from normal in erythrocyte and leucocyte cell counts,
    haemoglobin, haematocrit, differential leucocyte count, BUN, serum
    total protein, bilirubin, cholesterol, Na+, K+, Cl-, Ca2+,
    phosphate, alkaline phosphatase, SGOT, SGPT, urine analyses for
    glucose, proteins, ketone bodies, bilirubin or blood. Hydronephrosis
    was noted unilaterally in one male rat in Group II and in one in Group
    III and bilaterally in one male rat in Group IV. Liver weights were
    raised in Groups II, III and IV. Relative weights of thyroid, heart,
    spleen, kidneys, adrenals and gonads were all within normal ranges.
    Histological examination of heart, stomach, jejunum, colon, liver,
    pancreas, kidneys, spleen, adrenals, thyroid, testes and ovaries
    revealed no abnormalities related to treatment with S. violaceoniger
    (IFREB No. 741008).

         A 90-day study with 4 groups each containing 10 male and 10
    female Sprague-Dawley rats was carried out with a high-protein feed
    and 10% invert sugar from different sources instead of drinking-water.
    The groups were as follows: I, control invert sugar; II, glucose

    isomerized with S. violaceoniger and refined; III, as II, but not
    refined; IV, as III plus 2.5% S. violaceoniger. There were no
    abnormalities in growth rates, feed and drink consumption,
    haematology, serum biochemistry, urine analysis or organ weights
    (observations as specified above for a 4-week study). Histological
    examination of aorta, heart, stomach (rumen and fundus), pylorus,
    liver (including special stains, pancreas, spleen, mesenteric nodes,
    kidneys, prostate, thyroid, adrenals, gonads and uterus revealed only
    commonly occurring lesions with no clustering within any of the
    treatment groups (IFREB No. 751013).


         No toxicologically significant effects were produced in rats by
    Streptomyces violaceoniger preparations in feed or drink in 2 well-
    designed and thorough short-term studies. However, information is
    required about the occurrence in nature of the microorganism from
    which the enzyme is obtained.


    Estimate of temporary acceptable daily intake for man

    Not specified.*


    Required by 1984.

         Information about the occurrence of Streptomyces violaceoniger
    in nature.


    *    The statement "ADI not specified" means that, on the basis of the
         available data (toxicological, biochemical, and other), the total
         daily intake of the substance, arising from its use or uses at the
         levels necessary to achieve the desired effect and from its
         acceptable background in food, does not, in the opinion of the
         Committee, represent a hazard to health. For this reason, and for
         the reasons stated in individual evaluations, the establishment of
         an acceptable daily intake (ADI) in mg/kg bw is not deemed


    Institut Français de Recherches et Essais Biologiques (IFREB), No.
         741008. Isomerized glucose produced from glucose. 1-Month
         innocuity trial in the rat of the end product and intermediate
         substances. Unpublished report submitted to WHO

    Institut Français de Recherches et Essais Biologiques (IFREB), No.
         751013. 3-Month oral toxicity study in the rat of a syrup of
         isomerized glucose. Unpublished report submitted to WHO

    See Also:
       Toxicological Abbreviations