Quantification of arbuscular mycorrhizal fungi (AMF) biomass in hairy root production systems

Abstract

The symbiotic relationship of arbuscular mycorrhizal fungi (AMF) with plants has gained early interest because it was found to improve plant growth and productivity immensely i.e. by enabling enhanced nutrient uptake, water absorption as well as improved resistance against pathogens. Thus, AMF represent promising alternatives as biofertilizers to outperform commercial chemical fertilizers used in agriculture to increase plant productivity. However, the development of a commercially viable bioreactor-based production system of AMF with root-organ cultures is complicated since analytical methods enabling accurate and reproducible product quantification and quality analysis within a feasible time, being crucial tools for process optimization, are lacking. Hence, it is essential to establish reliable and precise analytical methods of AMF to facilitate the assessment of its growth as well as reproduction kinetics and therefore allow further process optimization. The main focus of this work was put on the development and application of three analytical methods to enable AMF biomass quantification in hairy root (HR) production systems. Quantification was carried out either i) in form of spore AMF biomass (spore count) through 1) a novel image analysis based spore count method or ii) total fungal biomass as accessible through the chitin content, for which 2) a fluorometric assay and 3) an HPLC-based sugar quantification approach were established and compared. In the context of the second goal of the thesis, the practical use of image analysis as an analytical tool was demonstrated on the investigation of fungal growth kinetics to answer medium optimization questions in AMF/carrot HR co-culture. Here, the influence of the medium ́s aggregation state as well as the medium ́s phosphorous and sugar concentration on fungal growth were investigated, the latter one in a design of experiments (DoE) approach.