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KMID : 0380620070390040438
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Korean Journal of Food Science and Technology
2007 Volume.39 No. 4 p.438 ~ p.446
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Changes of Protein Profiles in Cheonggukjang during the Fermentation Period
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Ilyn Santos
Sohn Il-Young
Choil Hyun-Soo
Park Sun-Min
Ryu Sung-Hee
Kwon Dae-Young
Park Cheon-Seok
Kim Jeong-Hwan
Kim Jeong-Sang
Lim Jin-Kyu
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Abstract
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The fermented soybean product, cheonggukjang, is favored by many people, partly due to its bio-functional ingredients. Since the fermentation process of cheonggukjang is mediated by enzymes, including proteases, produced by microbes, analysis of the proteome profile changes in cheonggukjang during fermentation would provide us with valuable information for fermentation optimization, as well as a better understanding of the formation mechanisms of the biofunctional substances. The soluble proteins from cheonggukjang were prepared by a phenol/chloroform extraction method, in order to remove interfering molecules for high resolution 2-D gel analysis. Proteomic analysis of the cheonggukjang at different fermentation periods suggested that most of the soluble soy proteins were degraded into smaller forms within 20 hr, and many microbial proteins, such as mucilage proteins, dominated the soluble protein fraction. The proteomic profile of cheonggukjang was very different from that of natto, in terms of the 2-D gel protein profile. Among the separated protein spots on the 2-D gels, 50 proteins from each gel were analyzed by MALDI-TOF MS and PMF for protein identification. Due to database limitations with regard to soy proteins and microbial proteins, identification of the changed proteins during fermentation was restricted to 9 proteins for cheonggukjang and 15 for natto. From de novo sequencing of the proteins by a tandem MS/MS, as well as by database searches using BLASTP, a limited number of proteins were identified with low reliability. However, the 2-D gel analysis of proteins, including protein preparation methods, remains a valuable tool to analyze complex mixtures of proteins entirely. Also, for intensive mass spectrometric analysis, it is also advisable to focus on a few of the interestingly changed proteins in cheonggukjang.
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KEYWORD
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Cheonggukjang, proteomics, MALDI-TOF MS, de novo sequencing, soluble proteins
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