###### Editorial Note on [Part 173](/current/title-21/part-173?toc=1)

#### Editorial Note:

Nomenclature changes to part 173 appear at [61 FR 14482](https://www.federalregister.gov/citation/61-FR-14482), Apr. 2, 1996; [66 FR 56035](https://www.federalregister.gov/citation/66-FR-56035), Nov. 6, 2001; [66 FR 66742](https://www.federalregister.gov/citation/66-FR-66742), Dec. 27, 2001; and [81 FR 49896](https://www.federalregister.gov/citation/81-FR-49896), July 29, 2016.

#### § 173.357 Materials used as fixing agents in the immobilization of enzyme preparations.

Fixing agents may be safely used in the immobilization of enzyme preparations in accordance with the following conditions:

(a) The materials consist of one or more of the following:

(1) Substances generally recognized as safe in food.

(2) Substances identified in this subparagraph and subject to such limitations as are provided:

| Substances | Limitations |
| --- | --- |
| Acrylamide-acrylic acid resin: Complying with [§ 173.5(a)(1)](/on/2024-09-23/title-21/section-173.5#p-173.5(a)(1)) and [(b) of this chapter](/on/2024-09-23/title-21/section-173.5#p-173.5(b)) | May be used as a fixing material in the immobilization of glucose isomerase enzyme preparations for use in the manufacture of high fructose corn syrup, in accordance with [§ 184.1372 of this chapter](/on/2024-09-23/title-21/section-184.1372). |
| Cellulose triacetate | May be used as a fixing material in the immobilization of lactase for use in reducing the lactose content of milk. |
| Diethylaminoethyl-cellulose | May be used as a fixing material in the immobilization of glucose isomerase enzyme preparations for use in the manufacture of high fructose corn syrup, in accordance with [§ 184.1372 of this chapter](/on/2024-09-23/title-21/section-184.1372). |
| Dimethylamine-epichlorohydrin resin: Complying with [§ 173.60(a)](/on/2024-09-23/title-21/section-173.60#p-173.60(a)) and [(b) of this chapter](/on/2024-09-23/title-21/section-173.60#p-173.60(b)) | May be used as a fixing material in the immobilization of glucose isomerase enzyme preparations for use in the manufacture of high fructose corn syrup, in accordance with [§ 184.1372 of this chapter](/on/2024-09-23/title-21/section-184.1372). |
| Glutaraldehyde | Do. |
| Periodic acid (CAS Reg. No. 10450-60-9). | |
| Polyethylenimine reaction product with 1,2-dichloroethane (CAS Reg. No. 68130-97-2) is the reaction product of homopolymerization of ethylenimine in aqueous hydrochloric acid at 100 °C and of cross-linking with 1,2-dichloroethane. The finished polymer has an average molecular weight of 50,000 to 70,000 as determined by gel permeation chromatography. The analytical method is entitled “Methodology for Molecular Weight Detection of Polyethylenimine,” which is incorporated by reference in accordance with [5 U.S.C. 552(a)](https://www.govinfo.gov/link/uscode/5/552) and [1 CFR part 51](/on/2024-09-23/title-1/part-51). Copies may be obtained from the Office of Food Additive Safety (HFS-200), Center for Food Safety and Applied Nutrition, 5001 Campus Dr., College Park, MD 20740, 240-402-1200, and may be examined at the Dockets Management Staff (HFA-305), Food and Drug Administration, 5630 Fishers Lane, Rm. 1061, Rockville, MD 20852, 240-402-7500, between 9 a.m. and 4 p.m., Monday through Friday, or at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, call 202-741-6030, or go to: *<http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html>* | May be used as a fixing material in the immobilization of glucoamylase enzyme preparations from *Aspergillus niger* for use in the manufacture of beer. May be used as a fixing material in the immobilization of: 1. Glucose isomerase enzyme preparations for use in the manufacture of high fructose corn syrup, in accordance with [§ 184.1372 of this chapter](/on/2024-09-23/title-21/section-184.1372). 2. Glucoamylase enzyme preparations from *Aspergillus niger* for use in the manufacture of beer. Residual ethylenimine in the finished polyethylenimine polymer will be less than 1 part per million as determined by gas chromatography-mass spectrometry. The residual ethylenimine is determined by an analytical method entitled “Methodology for Ethylenimine Detection in Polyethylenimine,” which is incorporated by reference in accordance with [5 U.S.C. 552(a)](https://www.govinfo.gov/link/uscode/5/552) and [1 CFR part 51](/on/2024-09-23/title-1/part-51). Residual 1,2-dichloroethane in the finished polyethylenimine polymer will be less than 1 part per million as determined by gas chromatography. The residual 1,2-dichloroethane is determined by an analytical method entitled, “Methodology for Ethylenedichloride Detection in Polyethylenimine,” which is incorporated by reference in accordance with [5 U.S.C. 552(a)](https://www.govinfo.gov/link/uscode/5/552) and [1 CFR part 51](/on/2024-09-23/title-1/part-51). Copies may be obtained from the Office of Food Additive Safety (HFS-200), Center for Food Safety and Applied Nutrition, 5001 Campus Dr., College Park, MD 20740, 240-402-7500, or may be examined at the Dockets Management Staff (HFA-305), Food and Drug Administration, 5630 Fishers Lane, Rm. 1061, Rockville, MD 20852, 240-402-7500, between 9 a.m. and 4 p.m., Monday through Friday, or at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, call 202-741-6030, or go to: *<http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html>.* |

(b) The fixed enzyme preparation is washed to remove residues of the fixing materials.

[[48 FR 5716](https://www.federalregister.gov/citation/48-FR-5716), Feb. 8, 1983, as amended at [52 FR 39512](https://www.federalregister.gov/citation/52-FR-39512), Oct. 22, 1987; [55 FR 12172](https://www.federalregister.gov/citation/55-FR-12172), Apr. 2, 1990; [59 FR 36937](https://www.federalregister.gov/citation/59-FR-36937), July 20, 1994; [61 FR 4873](https://www.federalregister.gov/citation/61-FR-4873), Feb. 9, 1996; [61 FR 14245](https://www.federalregister.gov/citation/61-FR-14245), Apr. 1, 1996; [67 FR 42716](https://www.federalregister.gov/citation/67-FR-42716), June 25, 2002; [81 FR 5592](https://www.federalregister.gov/citation/81-FR-5592), Feb. 3, 2016; [88 FR 17723](https://www.federalregister.gov/citation/88-FR-17723), Mar. 24, 2023]