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Free fatty acids identified as antitryptic factor in soybeans fermented by Rhizopus oligosporus
Abstract:
The trypsin-inhibitory activity observed in cooked soybeans fermented by Rhizopus oligosporus (fungus used in tempeh fermentation) has been examined. The active compounds have now been isolated by ethanol extraction and thin-layer chromatography and have been identified as free fatty acids by infrared spectroscopy and gas-liquid chromatography. Oleic, lineoleic, and linolenic acids are primarily responsible for the increased trypsin-inhibiting activity of cooked soybeans after fermentation. The free fatty acids are liberated from oil in the soybeans by fungal lipase, and they differ from other reported soybean trypsin inhibitors that are protein in nature. Free fatty acids have been previously reported to inhibit various enzymes, such as glycolytic, glyconeogenic, lipogenic, and also proteolytic. Their effect appears to be a nonspecific type of inhibition. Further studies are required to determine their physiological relevance, if any.
Insights
Fermented soybeans show increased trypsin inhibition due to free fatty acids, not proteins. These fatty acids, like oleic acid, are released by fungal enzymes and may non-specifically inhibit other enzymes.
Area of Science:
- Biochemistry
- Food Science
- Microbiology
Background:
- Soybean fermentation by Rhizopus oligosporus (tempeh fermentation) results in observed trypsin-inhibitory activity.
- Traditional soybean trypsin inhibitors are protein-based.
Purpose of the Study:
- To identify the compounds responsible for the trypsin-inhibitory activity in fermented soybeans.
- To investigate the mechanism of this inhibition.
Main Methods:
- Ethanol extraction and thin-layer chromatography for compound isolation.
- Infrared spectroscopy and gas-liquid chromatography for compound identification.
- Analysis of specific fatty acids: oleic, linoleic, and linolenic acids.
Main Results:
- The active compounds responsible for trypsin inhibition were identified as free fatty acids.
- Oleic, linoleic, and linolenic acids were found to be primarily responsible for the increased activity.
- Fungal lipase liberated these free fatty acids from soybean oil.
- The identified inhibitors are distinct from known protein-based soybean trypsin inhibitors.
Conclusions:
- Free fatty acids, liberated by fungal lipase during fermentation, are the primary agents of trypsin inhibition in cooked soybeans.
- This inhibition mechanism differs from previously identified proteinaceous inhibitors.
- Free fatty acids exhibit non-specific enzyme inhibition, affecting various metabolic pathways.
- Further research is needed to ascertain the physiological significance of these findings.