Cultivation of Phanerochaete chrysosporium and production of lignin peroxidases in submerged stirred tank reactors

Abstract

Production of lignin peroxidases by Phanerochaete chrysosposorium in a submerged stirred tank reactor is affected by certain critical parameters, some of which have been investigated in the present paper. These factors are: inoculum, pellet size, certain organic compounds such as polypropylene glycol or polyethylene glycol, culture conditions and composition. A rich inoculum results in formation of small pellets, fast depletion of glucose, and no production of lignin peroxidase. Reduced inoculum size prolongs the development of the culture followed by an active so-called secondary phase. The activity of the culture, however, is just enough to decolorize the blue color of Remazol dye but not strong enough to show extracellular lignin peroxidase. The presence of polypropylene glycol (PPG), polyethylene glycol (PEG) or hexadecane in the culture activates the culture towards lignin peroxidase production. The favorable effect of PPG exists only in cultures made up with tap water and reduced inoculum size at pH 4.5. Trace elements but not vitamins may be left out of the medium without impairing lignin peroxidase-producing ability. The use of desalinated water leads not only to the absence of lignin peroxidase production but also to retardation in growth of the fungi, emphasizing the need for a systematic investigation of the culture medium. The experiments were conducted in a 42 l stirred tank reactor and scaled up to 300 l reactor. Constant impeller tip speed and constant gas flow rate are not sufficient criteria for upscaling of this system.