title: Proteolysis in tempeh-type products obtained with Rhizopus and Aspergillus strains from grass pea (Lathyrus sativus) seeds.
abstract: BACKGROUND
  Tempeh is a food product obtained from legumes by means of solid-state fermentation with Rhizopus sp. Our previous research proved that mixed-culture inoculum may also be successfully applied. The objective of present research was to study the proteolytic activity of R. microsporus var. chinensis and A. oryzae during tempeh-type fermentation of grass pea seeds, and the effect of inoculum composition on the protein level and in vitro protein bioavailability in products.
  
  
  METHODS
  Fermentation substrate were soaked and cooked grass pea seeds. Material was mixed with single- or mixed-culture inoculum, and incubated in perforated plastic bags at 30°C for 32 hrs. In the products, the proteolytic activity (pH 3, 5 and 7), glucosamine, total protein and free amino acids levels, as well as protein in vitro bioavailability and degree of protein hydrolysis were obtained.
  
  
  RESULTS
  The significant correlation was found between glucosamine content and proteolytic activity in grass pea seeds fermented with Rhizopus or Aspergillus. The activities of Rhizopus proteases were higher than Aspergillus ones, which corresponded with the degree of seed protein hydrolysis. Both strains showed the highest activity of protease at pH 3. Tempeh made with pure culture of Rhizopus had 37% protein of 69% in-vitro bioavailability. Mixed-culture fermentation improved nutritional parameters of products only when the dose of Aspergillus spores in the inoculum was equal and lower than that of Rhizopus. This process resulted in higher in-vitro bioavailability of protein, slightly more efficient protein hydrolysis and higher level of free amino acids, as compared to standard tempeh.
  
  
  CONCLUSIONS
  The activity of A. oryzae in tempeh-type fermentation is beneficial as long as it does not dominate the activity and/or growth of Rhizopus strain.
authors.affiliation: Department of Food Biotechnology, University of Agriculture in Krakow, Poland.
authors.forename: Anna
authors.initials: A
authors.lastname: Starzyńska-Janiszewska
authors.affiliation: Department of Food Biotechnology, University of Agriculture in Krakow, Poland.
authors.forename: Bożena
authors.initials: B
authors.lastname: Stodolak
authors.affiliation: Department of Food Biotechnology, University of Agriculture in Krakow, Poland.
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Wikiera
mesh_terms: D000596:Amino Acids / Q000032:analysis / Q000378:metabolism; D001230:Aspergillus / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism*; D004063:Digestion; D005285:Fermentation; D005511:Food Handling; D005656:Fungal Proteins / Q000302:isolation & purification / Q000378:metabolism; D005944:Glucosamine / Q000032:analysis / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007408:Intestinal Absorption; D027807:Lathyrus / Q000737:chemistry* / Q000382:microbiology; D009753:Nutritive Value; D010446:Peptide Fragments / Q000032:analysis / Q000378:metabolism; D010447:Peptide Hydrolases / Q000302:isolation & purification / Q000378:metabolism; D014674:Plant Proteins, Dietary / Q000032:analysis / Q000378:metabolism*; D011044:Poland; D059748:Proteolysis; D012233:Rhizopus / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism*; D055314:Seed Storage Proteins / Q000032:analysis / Q000378:metabolism*; D012639:Seeds / Q000737:chemistry* / Q000382:microbiology; D000067075:Vegetable Products / Q000032:analysis* / Q000382:microbiology
chemical_list: D000596:Amino Acids; D005656:Fungal Proteins; D010446:Peptide Fragments; D014674:Plant Proteins, Dietary; D055314:Seed Storage Proteins; D010447:Peptide Hydrolases; D005944:Glucosamine
keywords: Aspergillus oryzae; Rhizopus microsporus var. chinensis; protease activity; proteolysis; tempeh