Monoseptic growth of fungal lipase producers under minimized sterile conditions: Cultivation of Phialemonium curvatum in 350 L scale

Abstract

AbstractA disadvantage of most microbial production processes is the need for sterile techniques. The objective of this study was the development of a robust fungal system allowing monoseptic growth with a minimum of sterile technique in plastic barrels. Selective growth conditions were achieved by mineral salts medium, known for the cultivation of Botrytis cinerea, but containing rapeseed oil instead of glucose as the sole source of carbon and energy. Furthermore, pH 3 was adjusted. A screening of fungi suitable for that system revealed Phialemonium curvatum AW02 isolated from compost. P. curvatum AW02 was superior in comparison with four further fungal isolates because high titers of hydrophilic spores were found in submerged production. Second, a biofilm formation on plastic segments or moving beds made harvesting of the biomass comfortable. Cultivations with volumes of 100 or 350 L showed no contaminations by bacteria when all conditions were controlled. Two independent approaches showed the dependance of growth on lipases in the cultivation system. A B. cinerea strain knocked out in lip1 showed reduced growth in comparison to the wild type because the first catabolic step is the triglyceride hydrolysis. P. curvatum AW02 lipase activity was detected. More than 90% was found to be cell wall associated. Solid shear stress liberated two active proteins showing IEPs of 4.7 or 5.6.