Energetic efficiency of complex substrate utilization by trichoderma viride

Abstract

AbstractThe efficiency of carbon substrate utilization is evaluated as the thermodynamic efficiency (ηx) of microbial growth.Three methods based on mass‐energy balance are used for the efficiency studies of complex substrates (straw, plant juices, lye) utilization by microfungi Trichoderma viride. According to substrate and biomass balance ηx = 0.55, 0.37 and 0.36 for Trichoderma viride growth on alkali pretreated wheat straw during 23, 34 and 50 hours. Cellulose biodegradation increases with cultivation time. However, the efficiency of cellulose utilization for cell mass growth decreases at the same time. In accordance with oxygen‐balance calculations ηx = 0.75 and 0.71 for the same processes. The discrepancy in results from the above two methods probably can be explained by the following: Substrate and biomass balance gives underestimated results. Oxygen balance method includes the part of energy for extracellular product formation and therefore ηx can be overestimated. The efficiency of complex soluble substrate utilization (lye, green juice, deproteinized brown plant juice) tested by means of pulse method gives the values of ηx = 0.72 – 0.88. Similar high estimates of ηx in C‐limited batch culture are observed for soluble carbohydrates (glucose, galactose, lactose, xylose) but not for acetate. The pulse method is advantageous for testing the “true” efficiency of carbon substrate utilization in a definite physiological environment.