AGGREGATION OF SPORES AND BIOMASS OF PHANEROCHAETE-CHRYSOSPORIUM IN LIQUID CULTURE AND THE EFFECT OF ANIONIC POLYMERS ON THIS PROCESS

The process of pellet formation by Phanerochaete chrysosporium in shake-flask culture originated with the aggregation of spores in the early stages of incubation. Spore aggregation was reduced in 0.2% (w/v) Junlon (polyacrylic acid) or 0.2% (w/v) Hostacerin (sodium polyacrylate). The prevention of spore aggregation by polyacrylic acids was a function of polymer concentration, molecular weight and ambient pH. These results indicate that the mechanism of dispersal of fungal biomass in submerged culture by polyacrylic acid is due to a steric stabilization mechanism. However, fermenter cultures of P. chrysosporium (and Aspergillus niger) in medium containing 0.2% (w/v) Junlon could not sustain the biomass concentrations achieved in equivalent shake-flask cultures. Additionally, fermenter cultures of these two organisms exhibited severe accretion of biomass to the walls of the fermenter and, in the case of A. niger, large amounts of foam were produced by cultures in the presence of polymer. This accretion and foaming was not related to inoculum concentration, antifoam type or concentration, or culture volume, but in A. niger could be prevented by a fivefold increase in the concentration of mineral salts or trace elements in the medium. Mineral salts supplementation also resulted in attainment of biomass densities similar to those achieved in shake-flask cultures, suggesting that the presence of the polymer in fermenter cultures caused a trace-element limitation not observed in equivalent shake-flask cultures. Junlon and Hostacerin were shown to bind cations present in the growth medium.