Evaluation of plastic composite-supports for enhanced ethanol production in biofilm reactors

• Published in: Journal of Industrial Microbiology 1996, Vol.16 (4), p.241-248
• Main Authors: Kunduru, M.R, Pometto, A.L. III
• Format: Article
• Language: English
• Subjects: bioenergy; Biological and medical sciences; Bioreactors; Biotechnology; energy resources; Fundamental and applied biological sciences. Psychology; Methods. Procedures. Technologies; natural resources; Saccharomyces cerevisiae; Various methods and equipments; Zymomonas mobilis
• ISSN: 0169-4146; 1367-5435; 1476-5535
• DOI: 10.1007/bf01570028

Biofilms are a natural form of cell immobilization that result from microbial attachment to solid supports. Biofilm reactors with polypropylene composite-supports containing up to 25% (w/w) of various agricultural materials (corn hulls, cellulose, oat hulls, soybean hulls or starch) and nutrients (soybean flour or zein) were used for ethanol production. Pure cultures of Zymomonas mobilis, ATCC 31821 or Saccharomyces cerevisiae ATCC 24859 and mixed cultures with either of these ethanol-producing microorganisms and the biofilm-forming Streptomyces viridosporus T7A ATCC 39115 were evaluated. An ethanol productivity of 374 g L-1 h-1 (44% yield) was obtained on polypropylene composite-supports of soybean hull-zein-polypropylene by using Z. mobilis, whereas mixed-culture fermentations with S. viridosporus resulted in ethanol productivity of 147.5 g L-1 h-1 when polypropylene composite-supports of corn starch-soybean flour were used. With S. cerevisiae, maximum productivity of 40 g L-1 h-1 (47% yield) was obtained on polypropylene composite-supports of soybean hull-soybean flour, whereas mixed-culture fermentation with S. viridosporus resulted in ethanol productivity of 190 g L-1 h-1 (35% yield) when polypropylene composite-supports of oat hull-polypropylene were used. The maximum productivities obtained without supports (suspension culture) were 124 g L-1 h-1 and 5 g L-1 h-1 with Z. mobilis and S. cerevisiae, respectively. Therefore, for Z. mobilis and S. cerevisiae, ethanol productivities in biofilm fermentations were three- and eight-fold higher than suspension culture fermentations, respectively. Biofilm formation on the chips was detected by weight change and Gram staining of the support material at the end of the fermentation. The ethanol production rate and concentrations were consistently greater in biofilm reactors than in suspension cultures.