γ‐Decalactone Production by Trichoderma harzianumin Stirred Bioreactors

Abstract

AbstractProduction of γ‐decalactone, a compound having peach‐like aroma characteristics, by a strain of Trichoderma harzianumis reported here for the first time. Cultures were carried out in a 14 L fermentor using castor oil as the sole carbon source. The filamentous‐like growth of the microorganism resulted in highly viscous and non‐Newtonian broths, which caused the formation of stagnant zones in the fermentor. T. harzianum was able to produce 260 mg/L of γ‐decalactone after 7 days of culture in a stirred fermenter operated at 3.3 s−1 and 1 vvm of air flow rate. The production of γ‐decalactone was mainly non‐growth associated. The use of high agitation rates—to improve mixing—resulted in celullar lysis. Cell damage occurred at volumetric power drawn as low as 0.2 W/L. Mycelial morphology (mainly hyphal thickness) changed drastically along the culture and was an important influence on the rheology of the broths. All these characteristics make this system an interesting model of study of hydrodynamically complex fermentations involving up to four phases.