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Candida guilliermondii Y4 is capable of synthesizing two different alcohol dehydrogenases. ADH1 is constitutive on different carbon sources under shaking or settling conditions and its activity is prominent on gel electrophoresis. ADH2 is only synthesized under shaking condition. Two types of mutants were isolated using an allyl alcohol selection technique. ADH1-deficient mutants had 2.7% ADH activity of the wild type, while ADH2-deficient mutants had an ADH activity as high as that of the wild-type ADH activity. The alcohol dehydrogenases of the mutants differ from those of the wild type in their relative oxidation rates of alcohols. ADH1 appears to possess a functional role mainly in the production of ethanol from acetaldehyde, while ADH2 functions mainly in the oxidation of ethanol to acetaldehyde. However, both enzymes seem to be capable of carrying out the reverse reactions, since mutants lacking either of them still grew satisfactorily on different carbon sources. Key words: Candida guilliermondii, alcohol dehydrogenase, ADH1-deficient mutant, ADH2-deficient mutant.

Alcohol dehydrogenase (ADH1) was purified from Candida guilliermondii strain B10-05 to homogeneity, using affinity chromatography on triazine dyes and gel filtration. The enzyme was tetrameric, with a subunit molecular weight of 38 000. The purified enzyme oxidized primary and secondary alcohols, although it preferred primary alcohols. Its activity toward secondary alcohols was better than those of other yeast ADH; however, the enzyme was less sensitive toward inhibitors. Kinetic studies indicated that C. guilliermondii ADH1 oxidized ethanol by an ordered bi–bi mechanism, with NAD as the first substrate fixed. Key words: Candida guilliermondii, alcohol dehydrogenase, ADH1, tetrameric.

Tempe merupakan makanan sehat dikarenakan kandungan komponen bioaktif dan merupakan sumber protein bagi vegetarian. Selama proses fermentasi, jamur tempe akan menghasilkan enzim protease yang memecah protein biji menjadi peptida bioaktif. Jenis jamur tempe dan lama fermentasi akan mempengaruhi peptida bioaktif yang terbentuk. Penelitian ini bertujuan untuk mengetahui pengaruh ragi tempe Raprima terhadap perubahan konsentrasi peptida dan pola protein selama fermentasi tempe koro benguk. Hasil penelitian menunjukkan aktivitas proteolitik mengalami kenaikan cepat pada awal fermentasi tempe dan mencapai aktivitas optimumnya pada fermentasi jam ke-96 sebesar 0,046 U/mL. Tempe mengalami perubahan pH dari awalnya sebesar 7,01 kemudian turun menjadi 5,92 pada fermentasi jam ke-30 dan kemudian naik kembali sampai dengan pH 7,25 pada akhir fermentasi (120 jam). Kadar peptida mengalalami peningkatan seiring dengan bertambahnya waktu fermentasi. Derajat hidrolisis meningkat cepat sampai 24 jam fermentasi kemudian mulai stabil pada jam 96 (46,31%). Pengamatan dengan SDS PAGE memperlihatkan terbentuknya protein/peptida dengan berat molekul < 25 kDa hasil hidrolisis protein koro benguk selama fermentasi menggunakan ragi Raprima.

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Purpose The purpose of this paper is to understand the effect of hydrolysis by pepsin and pancreatin on the angiotensin-I-converting enzyme (ACE) inhibitory activity of bioactive peptide from pigeon pea tempe and the absorption of pigeon pea tempe peptide by using the everted gut sac method. Design/methodology/approach The tempe was prepared by inoculating Raprima (Rhizopus oligosporus) on hulled-cooked pigeon pea for 48 h. The extraction was performed using the ultrasonic method at 40 kHz frequency and 100% ultrasonic power for 10 min. The extracted protein was placed in simulated gastrointestinal digestion using consecutive pepsin–pancreatin for 240 min. The hydrolysates were fractionated using a dialysis tube, and its absorption was assessed using the everted Sprague–Dawley rat gut sac. Findings The tempe protein from the hydrolyzed pigeon pea exhibited higher ACE inhibitory (71.53%) activity than that from the boiled pigeon pea (53.04%) (p = 0.028). The bioactive peptide of the digested pigeon pea tempe consisted of low-molecular-weight peptides (<1 kDa). The fraction also showed the highest ACE inhibition activity among the others (IC50 = 0.61 mg/mL, p = 0.021). Bioactive peptides from pigeon pea tempe were absorbed well in the small intestine, mainly in the jejunum. The activity of the absorbed peptides did not change considerably. Originality/value The activity of bioactive peptide of pigeon pea tempe was comparatively stable during digestion. It exhibited activity even after absorption in the small intestine. Thus, pigeon pea tempe can serve as an antihypertensive peptide source and alternative food for maintaining/reducing blood pressure.