Application of Waste Activated Bleaching Earth Containing Rapeseed Oil on Riboflavin Production in the Culture of Ashbya gossypii H. Ming, Ana V. Lara Pizarro, and Enoch Y. Park* Laboratory of Biotechnology, Department of Applied Biological Chemistry, Faculty of Agriculture, Shizuoka University, 836 Ohya, Shizuoka 422-8529, Japan Waste activated bleaching earth (ABE) that contained 40% rapeseed oil and was discharged by an oil refinery plant, was used for riboflavin production in a culture of Ashbya gossypii. When 125 g/L waste ABE that contained 50 g/L rapeseed oil was added into the culture, the riboflavin concentration was 1.12 g/L, which was almost 1.6-fold as high as that of pure rapeseed oil. However, in waste ABE concentration higher than 125 g/L, the produced riboflavin concentration decreased, which was due to the difficulty in mixing due to the presence of a high amount of solid material in the culture. The surface of the waste ABE was smooth without a hitch, because of being covered with rapeseed oil. However, after the culture, the surface of the waste ABE seemed like that of new one, and the oil content was nearly zero grams per liter. The waste ABE, oily clay, and its black color gradually fade and yellow little by little, and finally the waste ABE changed to yellow powder. Of the riboflavin produced during the culture, 70% was adsorbed in the oil free waste ABE. With diluted alkali solution, extraction only two times yielded 90% recovery of riboflavin adsorbed in the waste ABE. The waste ABE containing waste vegetable oil was suitable for raw material for production of the value-added useful bioproducts, which might be a good model for reuse of the waste resource. Introduction Awareness of environmental problems and potential hazards generated by industrial manufacturers has prompted many countries to limit the discharge of polluting materials. The manufacture of vegetable oil yields two kinds of waste disposals: large quantities of black and highly pollutant wastewater, designated as oil- mill wastewater; solid waste disposals containing waste vegetable oil. The effluent is characterized by a high polluting load, due to high content of organic substances and because of a high toxicity toward several biological systems (1-3). To detoxify or to decolorize this oil-mill effluents, anaerobic treatment (4), methane production (5), use of white-rot fungi (6) or yeast (7), and a compost- ing process (8) have been employed. As for solid waste disposals containing waste vegetable oil, one of them, an enormous amount of activated bleaching earth (ABE) is discarded by crude oil refining industries. This ABE has been used for adsorbing the dark color or odor of crude oil, which is caused by chro- mophoric chloroplast-related materials with different degrees of polymerization. During this oil refinery process the waste ABE adsorbs 40% of vegetable oil on a weight basis. Japan alone annually discharges more than 50 000 metric tons. Recently the waste ABE discharged from the oil refinery process has been passed to the cement industry for incineration, but a cement manufacturer has a lot of difficulty in treating the waste ABE, because it contains waste vegetable oil, to fit the requirements of the cement’s quality. Moreover, in the near future the incineration or landfill disposal is probably impossible, because of environmental restrictions, spoiling of released waste oil, lack of suitable new sites, and green house effect. However, there are no reports about biological treat- ment of the solid waste disposals containing waste vegetable oil. Here we tried to convert the vegetable oil contained in the waste ABE into useful value-added bioproducts using oil-utilizing microorganisms. The veg- etable oil-utilizing microorganism Ashbya gossypii (A. gossypii) is a popular high-yield riboflavin producer. In the early 1980s, the world consumption of riboflavin had been reported to be 1250 tons for human and animal uses (2). At present, the amounts of riboflavin production are * To whom correspondence should be addressed. Phone: +81-54-238-4887. Fax: +81-237-3028. E-mail: yspark@agr. shizuoka.ac.jp. Table 1. Physicochemical Properties of Activated Bleaching Earth chem composition (% based on drying at 110 °C) Ig loss 5.2 SiO2 79.8 Al2O3 8.7 Fe2O3 1.9 MgO 3.2 CaO 0.7 moisture (%) 10.0 fineness (% pass through 90 μm sieve) 94.5 specific surface area (m 2 /g) 290 residual acidity (mg of KOH/g) 0.9 bulk density (g/mL) 0.7 true specific gravity 2.4 410 Biotechnol. Prog. 2003, 19, 410-417 10.1021/bp0257325 CCC: $25.00 © 2003 American Chemical Society and American Institute of Chemical Engineers Published on Web 12/28/2002