Mass production of spores of lactic acid-producing Rhizopus oryzae NBRC 5384 on agar plate

Authors

  • Tsuneo Yamane,

    Corresponding author
    1. Department of Environmental Bioscience, College of Bioscience and Biotechnology, Chubu University, Kasugai City, Aichi Prefecture, Japan
    Search for more papers by this author
  • Ryosuke Tanaka

    1. Department of Environmental Bioscience, College of Bioscience and Biotechnology, Chubu University, Kasugai City, Aichi Prefecture, Japan
    Current affiliation:
    1. Amano Souken Co., Ltd., Nagoya City, Aichi Pref., Japan
    Search for more papers by this author

Abstract

Mass production of sporangiospores (spores) of Rhizopus oryzae NBRC 5384 (identical to NRRL 395 and ATCC 9363) on potato-dextrose-agar medium was studied aiming at starting its L(+)-lactic acid fermentation directly from spore inoculation. Various parameters including harvest time, sowed spore density, size of agar plate, height of air space, and incubation mode of plate (agar-on-bottom or agar-on-top) were studied. Ordinarily used shallow Petri dishes were found out to be unsuitable for the full growth of R. oryzae sporangiophores. In a very wide range of the sowed spore density, the smaller it was, the greater the number of the harvested spores was. It was also interesting to find out that R. oryzae grown downward vertically with a deep air space in an agar-on-top mode gave larger amount of spores than in an agar-on-bottom mode at 30°C for 7-day cultivation. Scale-up of the agar plate culture from 26.4 to 292 cm2 was studied, resulting in the proportional relationship between the number of the harvested spores/plate and the plate area in the deep Petri dishes. The number of plates of 50 cm in diameter needed for 100 m3 industrial submerged fermentation started directly from 2 × 105 spores/mL inoculum size was estimated as about 6, from which it was inferred that such a fermentation would be feasible. Designing a 50 cm plate and a method of spreading and collecting the spores were suggested. Bioprocess technological significance of the “full-scale industrial submerged fermentation started directly from spore inoculation omitting pre-culture” has been discussed. © 2013 American Institute of Chemical Engineers Biotechnol. Prog., 29:876–881, 2013

Ancillary