Tadayoshi Tazaki

Growth and respiratory activity of mold fungus (Trichoderma lignorum)

The growth ofTrichoderma lignorum was studied in relation to the carbon balance of the culture system and the respiratory activity at different growth phases.Conidia, after inoculation into the medium, swelled and germinated rapidly. The growth rate of the hyphae at the exponential phase was 0.46 hr−1 (2.2 hr for mass doubling) at 25 C. The yield efficiency of hyphal biomass-C at the cost of glucose-C was 67%, while those of the waste products-C excreted and of CO2-C evolved were, 6.5% and 26.5%, respectively. The yield efficiency of conidia-C to the decrease of hyphae-C was 34%. The germination, growth rate and carbon balance were not affected by different concentrations of glucose from 10 to 2×103 mg glucose-C/l.Carbon dioxide was needed as the growth factor for the initiation of the germination of conidia, but there was no increase in yield efficiency as a result of CO2 fixation.The respiratory rate of the fungus changed drastically as the growth proceeded. The rate of endogenous respiration of conidia was less than 0.2 mg CO2-C/g conidia-C/hr which increased immediately after inoculation into the medium. The highest respiratory rate of hyphae (100–110 mg CO2-C/g hyphae-C/hr) was obtained throughout the exponential phase. Thereafter, decreasing rapidly, the respiratory rate of submerged hyphae of 1-week-old showed only 1.8 mg CO2-C/g biomass-C/hr, whereas the rate of aerial hyphae forming conidia increased again, but did not exceed 10 mg CO2-C/g biomass-C/hr.