Affiliation:
1. Department of Food Science and Human Nutrition, Center for Crops Utilization Research, Iowa State University, Ames, Iowa 50011
Abstract
Novel solid supports, consisting of polypropylene blended with various agricultural materials (pp composite), were evaluated as supports for pure- and mixed-culture continuous lactic acid fermentations in biofilm reactors.
Streptomyces viridosporus
T7A (ATCC 39115) was used to form a biofilm, and
Lactobacillus casei
subsp.
rhamnosus
(ATCC 11443) was used for lactic acid production. For mixed-culture fermentations, a 15-day continuous fermentation of
S. viridosporus
was performed initially to establish the biofilm. The culture medium was then inoculated with
L. casei
subsp.
rhamnosus.
For pure-culture fermentation,
L. casei
subsp.
rhamnosus
was inoculated directly into the reactors containing sterile pp composite chips. The biofilm reactors containing various pp composite chips were compared with a biofilm reactor containing pure polypropylene chips and with a reactor containing a suspension culture. Continuous fermentation was started, and each flow rate (0.06 to 1.92 ml/min) was held constant for 24 h; steady state was achieved after 10 h. Lactic acid production was determined throughout the 24-h period by high-performance liquid chromatography. Production rates that were two to five times faster than those of the suspension culture (control) were observed for the pure- and mixed-culture bioreactors. Both lactic acid production rates and lactic acid concentrations in the culture medium were consistently higher in mixed-culture than in pure-culture fermentations. Biofilm formation on the chips was detected at harvest by chip clumping and Gram staining.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
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