Sludge sample was collected from

Microscope pictures of straw tissues before the inoculation stage (day 0) were presented in Supplementary Information – Fig. S2. The wheat straw structure was overall undegraded, with intact cell walls and a near absence of microorganisms within straw tissues. Essentially, three kinds of tissue were visible: the parenchyma, sclerenchyma and epidermis. Parenchyma Cabozantinib displayed thin cell walls mainly composed of a middle lamella, a primary wall and a large cell lumen (Fig. S2–P0%) which are known to be highly lignified (Nougarède et al., 1969). Sclerenchyma cells display a thick secondary wall of a few micrometers (Fig. S2–S0%). The epidermis presented a thick secondary wall and highly lignified cells (Fig. S2–E0%). In addition, as mentioned in the literature (Sun, 2010), a waxy layer, the cuticle covers the outward-facing cell wall. The epidermis is also characterized by its high silica content, revealed in TEM as grainy texture when associated with organic carbon or as crystallized particles (Watteau and Villemin, 2001). This observation was checked by Electron Dispersive X-ray analyses (EDX), where high amounts of silica were associated to the cuticle cell walls (Supplementary Information Fig. S3). Lastly, the inoculum (not shown) was composed of cell membrane residues, residual organic matter coming from the industrial digestate, and a large variety of microorganisms (great diversities of microbial shapes and sizes) which is in adequacy to literature (Abbassi-Guendouz et al., 2013 and Shi et al., 2013).