Abstract
In order to reduce the production cost of bioflocculants we proposed to utilize acetic and/or propionic acids, which can be produced from organic wastes by anaerobic digestion, as the substrates for the bioproduction. To realize this strategy, bacterial strains which can produce kaolin-flocculating agents (bioflocculants) from acetate and/or propionate were screened from various environmental sources. Four bacterial strains which showed especially effective flocculating activity were named TKF01, TKF02, TKF03 and TKF04 and identified as Enterobacter sp., Acinetobacter sp., Haemophilus sp. and Citrobacter sp., respectively, according to their morphological and physiological properties. The optimum temperature and pH for the biofocculant production were approximately 30°C and 7.0-8.0, respectively, for all the strains. They could utilize some organic acids, sugars and/or alcohols for their growth, however, acetate was the most effective substrates for bioflocculant production. The bioflocculants were found to be effective for the flocculation of a kaolin suspension in wide range of pHs (2.0-10.0) and temperatures (ca.10-80°C), while the co-presence of cations (Na+, K+, Ca2+, Mg2+ etc.) did not enhance the flocculating activity. Two of the bioflocculants could flocculate a variety of suspended p articles including kaolin, diatomite, bentonite, activated carbon, soil and activated sludge, while the other 2 were effective for limited ranges of particles, only kaolin and diatomite or soil. The results suggested that various types of bioflocculants can be produced from acetate and/or propionate, although no report has described bioflocculant production from these substrates so far.
