THE INDIVIDUAL AND COMBINED INFLUENCE OF TEMPERATURE, TIME, PH AND COD CONCENTRATION ON THE BIODEGRADATION ACTIVITIES OF SELECTED BACTERIALSTRAINS GROWN ON RAW BAKERS-YEAST EFFLUENT

Five bacterial strains (Chryseomonas luteola, Fusobacterium mortiferum , Enterobacter agglomerans, Klebsiella oxytoca and and unidentified Gr am-negative rod) were grown on raw baker's yeast effluent to assess th e influence of environmental factors on biodegradation processes. A 3x 4x3 factorial design was used to determine the effects of time, pH and COD concentration, at four different temperatures. Total volatile fat ty acid production was chosen as the most representative indicator of biodegradation. Results showed that the strains differed greatly in th eir ability to produce anaerobic digester intermediary metabolites, un der defined environmental conditions. The study showed that the degrad ation of the complex compounds in baker's yeast effluent could be enha nced by changing environmental factors. The most positive responses we re obtained at the higher COD concentrations (30 g l(-1)), the higher pH values (6.0), and after 24 to 48h incubation time and at the higher temperatures (35 degrees C). The most positive effect (+355.00) was f ound for Chryseomonas luteola at a 48h incubation time, COD concentrat ion of 30 g l(-1), pH of 6.0 and temperature of 35 degrees C. The vola tile fatty acid yields obtained by the strains differ from the statist ical indications, but provide a valuable reference of the actual conce ntrations obtained by the experimental study. The factorial design rep resented the effects of environmental changes, while the quantitative TVFA data set gave experimental data. This study showed that the manip ulation of various environmental factors in biologically controlled sy stems, such as anaerobic digesters, could further enhance the biodegra dation efficiency of the microbial population in the raw effluent.