Growth and influence of white-rot fungi on the chemical composition of wheat straw inoculated under varying pre-conditions

Abstract

Solid-state fermentation with white-rot fungi is an interesting alternative to chemical straw treatment for ruminant nutrition. However, for practical implementation on farms, feasible handling and its effect on nutritional characteristics have to be tested beforehand. Chopped wheat straw was either soaked and drained or just remoistened to about 24% dry matter without subsequent sterilization. Moist straw was inoculated with Pleurotus ostreatus, Ceriporiopsis subvermispora, or Volvariella volvacea. Fermentation lasted up to 42 d with weekly or shorter sampling intervals. Fiber fractions, minerals and elements, and non-starch polysaccharides were analyzed, and microflora was plate counted. Lactic acid bacteria of selected samples were identified by MALDI-TOF. All inoculated fungi grew well under the selected conditions expressed by the visible mycelium and specific smell. P. ostreatus developed fruiting bodies in the given time. Initial numbers of lactic acid bacteria were >8.0 log cfu/g. In the beginning, Weissella confusa/cibaria dominated. However, neither decrease in lignin nor cellulose concentration was observed during the period in either of the treatments, thus seeming to be inappropriate for ruminant nutrition purposes. Some elements and minerals peaked, especially towards the second and third week (Na, Cl, Mg, Fe, and Mn). Growth conditions for mushrooms were optimized by remoistening the straw with a defined amount of water.