Micropropagule production from Trichoderma harzianum EGE-K38 using solid-state fermentation and a comparative study for drying methods

Abstract

In this study, Trichoderma harzianum EGE-K38 was used for micropropagule production in solid-state fermentation. Various inexpensive agricultural co-products including wheat bran, sawdust, rice straw, hazelnut shell, grape marc, and cotton seed cake were tested as natural substrates, and zeolite was tested as an inert support for micropropagule production. Several parameters were determined to obtain maximum micropropagule production: the effects of various nitrogen sources, initial moisture content, initial pH, incubation temperature, and incubation time. Maximum micropropagule count achieved was (1.30 ± 0.68) × 10^{10} cfu/g dry substrate with a wheat bran-malt sprout mixture (3:2), at 28 °C, an initial moisture content of 70% (w/w), and an initial pH of 5.8 ± 0.3 after 4 days of cultivation. In zeolite-based medium, a maximum micropropagule count of (5.12 ± 0.61) × 10^8 cfu/g dry inert support was achieved. Optimized parameters were used in a higher scale where micropropagules were produced in trays using a wheat bran-malt sprout medium and harvested to determine the drying conditions in both lyophilization and oven-drying. It was found that up to 97% of micropropagules retained their viability with glycerol as a protectant after 1 day of oven-drying at 40 °C.