Microbial and volatile organic compound profiles of peat and bark-based casing materials in Agaricus bisporus cultivation

• Microbial community composition is dynamic in conventional and alternative casing materials. • Pseudomonas species dominate casing microbiota. • VOC profile differs significantly between peat and bark-based casing materials. • Fungi-associated volatiles are prevalent in bark-based casing. Peat has a central function in the commercial cultivation of Agaricus bisporus (button mushrooms). However, peat-use faces scrutiny due to the environmental damage caused by extraction. The identification and assessment of sustainable alternatives to peat is an active area of research. Despite this, little is known about how alternative casing materials differ in microbial community composition and volatile organic compound (VOC) profiles, both of which are known to have a profound influence on mushroom development. This study aimed to characterise and compare the microbiota and VOC profiles of two novel bark-based casing alternatives and a commercial peat control over the course of a mushroom production cycle. It was found that all treatments supported comparable microbial diversity. Important bacterial genera, including Pseudomonas , were identified across all treatments. Meanwhile, VOC composition varied significantly between peat and bark-based casing. In particular, bark-based casings had higher levels of 1-octen-3-ol and 3-octanone, which may influence primordia formation and disease suppression. These findings highlight the necessity for further research into the functional roles of casing microbiota and VOCs. Addressing these knowledge gaps will be vital in the development of effective peat-free casing alternatives.