VETERINARY MICROBIOLOGY (POSTER PRESENTATION) E¡ect of Fishing Industries E¥uents pH and Organic Load on the Methanogenic Bacteria Bio¢lm Developed over Support in Fixed Biomass Reactor H. Urrutia 1 , R.Vidal 1 , M. Baeza 1 , andE. Aspe¨ 2 1 Departamento de Microbiologia, Facultad de Ciencias Biolo Âgicas, Universidad de Concepcio Ân, Chile; 2 Departamento de Ingenierõ Âa Quõ Âmica, Facultad de Ingenierõ Âa, Universidad de Concepcio Ân, Chile Key Words: Methanogenesis, bacterial adherence, biofilm growth, anaerobic digestion The effect of pH and organic matter (total organic carbon, TOC) of effluents originating from fishing industries located in Talcahuano, Chile, on the ability to colonize different trophic group methanogenic bacteria (MB) over clay and polyethylene supports was evaluated. Both support materials enhanced all types of methanogenic bacterial growth compared to systems without support. The highest adherence was obtained at pH 8. At 8000 mg/ l TOC, this had a significant effect on the growth rate of hydrogenotropic and methylaminotrophic methanogens on polyethylene and clay, respec- tively. # 1999 Academic Press Introduction Anaerobic digestion of fishing industries effluents is severely limited by their sulfate concentration [1]. In order to improve the anaerobic bacterial activity rate inert supports have been used to produce cellular immobilization. In these systems, bacterial activity is regulated by bacterial growth rate and adherence properties as well as by some environmental condi- tions [2]. In this study the effect of pH and organic matter concentration in the early stages of methano- genic bacteria biofilm formation over two types of inert support was studied. Materials and Methods Clay spheres (5 mm diameter) and polyethylene Bioblock (4 mm diameter 6 8 mm length) support were carried out in batch tests using 50 ml vials containing 5 ml of supporting material and 25 ml of a model fish effluent. Vials without support were also included as control. Once the pH was adjusted to 5.0, 7.0 and 8.0, vials were tightly closed with butyryl stoppers, sealed with aluminum caps, autoclaved, inoculated with 0.5 ml of sludge (from anaerobic reactor) and incubated at 308C for 35 days under constant shaking (120 rpm). The gas phase methane concentration was measured by gas chromatography (HACH, Co., U.S.A.). Samples with support were processed in anaerobic box under N 2 ±CO 2 (80%±20%) (LabConco) atmosphere. Non-adhered bacteria were removed by repeated rinsing with anaerobic mineral salt solution [3]. Then, support samples were Corresponding author: Homero Urrutia Briones, Departamento de Microbiologõ Âa, Facultad de Ciencias Biolo  gicas, Universidad de Concepcio Ân, Casilla 152-C. Fax: (56-41-245975). E-mail: hurrutia@udec.cl 1075±9964/99/030325 + 03 $30.00/0 # 1999 Academic Press Anaerobe (1999) 5, 325±327 Article No. anae.1999.0301