Factors influencing the activity of sterile filtered and heat-sterilized trypsin solutions

Our plain-English summary of Factors influencing the activity of sterile filtered and heat-sterilized trypsin solutions, by R.A. Cook, G.M. Poole (Applied Microbiology, 1974).

The study

• Authors: R.A. Cook, G.M. Poole
• Journal: Applied Microbiology
• Published: 1974;28(1):154-5
• Read it: PubMed · Publisher · Free full text

Abstract

The mode of sterilization (filtration or heat) was found to significantly affect the activity of trypsin solutions. Trypsin activity was substantially reduced in the initial fractions of filtrate passed through asbestos filter pads; heat-sterilized trypsin was satisfactory for transfer of cell cultures grown on glass. Heat-sterilized trypsin may be useful when elimination of filterable organisms is required.

In plain English

This short laboratory report from Eli Lilly and Company in Greenfield, Indiana, examined how the way trypsin solutions (an enzyme used to detach cultured cells) were sterilized affected their activity. It did not study human health or disease. A 100-liter lot of 0.25% trypsin was filtered through Seitz presses fitted with asbestos pads. Samples from the first 40 liters of filtrate had substantially less activity than later portions. In a second lot, trypsin activity was 1.37 mg/ml before filtration, 1.19 to 1.30 mg/ml after membrane filtration, and 0.80 mg/ml in the first 20 liters passed through asbestos pads. The authors concluded that asbestos pads are not suitable for sterile filtration of trypsin solutions. The authors also tested heating trypsin in acid solution that had been seeded with Bacillus subtilis spores. No bacterial growth was observed after heating. The heated trypsin harvested a monkey kidney cell line for five passages without observed toxicity. In a preliminary experiment, however, heated trypsin yielded fewer rabbit kidney cells than membrane-filtered trypsin.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory experiment reported as a short note, comparing the enzyme activity of trypsin solutions sterilized by asbestos-pad filtration, membrane filtration, or heat
• Who was studied: Trypsin solutions prepared at Eli Lilly and Company, Greenfield, Indiana: two 100-liter lots of 0.25% trypsin, plus a 1-liter heat-sterilization test solution. Cells used were the BS-C-1 green monkey kidney cell line and rabbit kidneys. No people were studied.
• Exposure: Filtration of trypsin solutions through asbestos filter pads (Type ST-3) in Seitz presses, compared with membrane filtration and with heat sterilization at pH 2.3. No fiber type is named.
• Main results:
  • In the first lot, samples from bottles A and B (the first 40 liters of filtrate through asbestos pads) had substantially less trypsin activity than samples from bottles C, D and E.
  • In the second lot, trypsin activity was 1.37 mg/ml before filtration and 0.80 mg/ml in the first 20 liters of Seitz (asbestos-pad) filtrate. It was 1.16 mg/ml in the second 20 liters of Seitz filtrate.
  • In the second lot, membrane-filtered portions had trypsin activity of 1.19 mg/ml (1st 20 liters), 1.29 mg/ml (2nd 20 liters) and 1.30 mg/ml (last 13.5 liters).
  • After the authors reduced lot size to 50 liters and switched to membrane filtration, bottle-to-bottle differences in trypsin activity were considerably reduced.
  • Trypsin solution seeded with Bacillus subtilis spores, adjusted to pH 2.3 and heated, produced no bacterial growth. Unheated acidified controls showed a confluent lawn of growth.
  • Heated trypsin was used to harvest BS-C-1 monkey kidney cells for five consecutive passages, and no cell toxicity was observed.
  • In a preliminary experiment, rabbit kidneys extracted with heated trypsin yielded 1.35 ml of packed cells, compared with 3.10 ml with membrane-filtered trypsin.
• The authors' conclusion: The authors concluded that asbestos pads are not suitable for sterile filtration of trypsin solutions. They stated that heat-sterilized trypsin was satisfactory for transfer of cell cultures grown on glass.
• Limitations the authors state:
  • The authors described the rabbit kidney cell-yield comparison as preliminary. They suggested the lower yield with heated trypsin may be due to loss of other enzymes during heat sterilization.
  • The authors noted that occasional lot-to-lot differences in trypsin activity were caused by variation in the potency of commercially obtained trypsin.

Topics

Medical terms in this study, explained in our Lexicon: Filter pad.

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