Introduction

Anaerobic fungi firstly classified as fungi in the 1980s by Orpin are phylogenetically confined as a whole in the phylum Neocallimastigomycota since 2007. These organisms had to undergo exceptional adaptation to their hosts digestive system, located in the rumen of herbivores. As primary digesters of lignocellulosic materials anaerobic fungi segregate a wide range of carbohydrate-active enzymes contained in cellulosomes. Additionally to enzymatic digestion physical disruption of plant cells through appressorium-like structures allow highly effective usage of chemically stable lignocellulosic materials. Growth is obtained through mixed acid fermentation, partially accomplished in hydrogenosomes, with the main products acetate, formate, ethanol, lactate, hydrogen, and succinate. Despite nearly 50 years of studies, the optimal cultivation conditions of Neocallimastigomycota remain unknown. Previously, only few physiological studies, focused on Neocallimastix and Piromyces were published. This study expands the currently known based on six genera isolated by Stabel et al.; 2020.

Goals

By gaining a deeper comprehension of cultivation conditions and fine-tuning the growth parameters of anaerobic fungi, we aim to enhance, the selectivity of preferred metabolites, reduce the costs and environmental problems associated with the exploitation of lignocellulosic materials for industrial use and facilitate the replacement of fossil fuels through generated hydrogen.

Materials & Methods

The used strains were cultivated in batches in serum flasks with deviating parameters. Soluble metabolites were analyzed by HPLC and H2 was analyzed by GC and pressure.

Results

Anaerobic fungi show specific tendencies in their metabolic pathway, which are able to slightly change depending on the cultivation conditions. Effects of different C-sources and concentrations, particle sizes, temperatures, batches and fed-batches reveal valuable insight.

Summary

Anaerobic gut fungi are promising organisms for H2 production from lignocellulose. The results indicate great potential for future application.