Viability of dry Trichoderma harzianum spores under storage

Abstract

Spores of the potential biocontrol agent Trichoderma harzianum P1 were prepared without (M1) and with heat shock (40 °C for 90 min) after fermentation (M2), filtered into a paste and dried over silica gel. M1 and M2 exhibited high viability (55%) and similar initial trehalose contents (4.0 and 5.4%, respectively) after slow drying. No significant differences in viability were found between treatments during storage for 110 days under different temperatures, T (8, 33 and 42 °C) and water activities, a _w (0.03, 0.33 and 0.75). Viability of spores, after storage at a _w =0.03 were 100 and 70% for 8 and 33 °C, respectively. During storage, decrease in trehalose content and viability was faster at a _w =0.75 and 42 °C. Loss of viability was modeled by a first order kinetic model depending on 1/T and a _w . M2 (with heat shock) showed slightly higher trehalose contents than M1 which resulted in 100% viability after 52 days at 8 °C.