Cultivable fungal growth and microbial community profiles during drying of earth-hemp composites
Abstract
Earth-hemp composites are promising low-carbon construction materials, but their wider use is limited by uncertainties regarding their susceptibility to microbial growth, particularly during drying. This study investigates cultivable fungal growth and microbial community profiles during the drying of composites manufactured with two earths exhibiting contrasting mineralogical and hydric properties: a kaolinite earth (K) and an illite-montmorillonite-chlorite earth (MIC). Materials were characterised using physicochemical analyses, fungal cultivation and DNA sequencing. The MIC and K earths had clay contents of 20.7% and 13.3%, respectively, and methylene blue values of 4.26 and 0.66 g/100 g, highlighting their contrasting clay reactivity. Initial cultivable fungal concentrations were approximately 3.2 log(CFU/g) in the MIC-based composite and 5.1 log(CFU/g) in the K-based composite. Despite this initial difference, both composites reached approximately 6 log(CFU/g) during the first eight days of drying, before decreasing or stabilising as gravimetric water content declined. DNA sequencing revealed shifts in microbial community composition. The two selected earths exhibited broadly similar bacterial community profiles under the tested conditions, while the communities detected in hemp shiv included taxa commonly associated with fibre degradation and retting. These results indicate an association between early fungal growth and the high moisture stage of drying, while the influence of mineralogy could not be isolated from differences in initial contamination and experimental conditions. The findings highlight the need to control the initial microbial load and drying kinetics and provide a framework for future studies combining direct water activity measurements, sterile controls and absolute microbial quantification.
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BibTeX
@article{taillade2026cultivable,
title = {{Cultivable fungal growth and microbial community profiles during drying of earth-hemp composites}},
author = {Eva Taillade and Thomas Verdier and Myriam Mercade and Pascale Lepercq and Sophie Claude and Hugo Cagnon and Jean-Emmanuel Aubert},
journal = {Journal of Building Engineering},
year = {2026},
month = oct,
doi = {10.1016/j.jobe.2026.117177},
url = {https://hal.inrae.fr/hal-05799872v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Cultivable fungal growth and microbial community profiles during drying of earth-hemp composites
AU - Eva Taillade
AU - Thomas Verdier
AU - Myriam Mercade
AU - Pascale Lepercq
AU - Sophie Claude
AU - Hugo Cagnon
AU - Jean-Emmanuel Aubert
PY - 2026
DA - 2026/10/14
JO - Journal of Building Engineering
DO - 10.1016/j.jobe.2026.117177
UR - https://hal.inrae.fr/hal-05799872v1
AB - Earth-hemp composites are promising low-carbon construction materials, but their wider use is limited by uncertainties regarding their susceptibility to microbial growth, particularly during drying. This study investigates cultivable fungal growth and microbial community profiles during the drying of composites manufactured with two earths exhibiting contrasting mineralogical and hydric properties: a kaolinite earth (K) and an illite-montmorillonite-chlorite earth (MIC). Materials were characterised using physicochemical analyses, fungal cultivation and DNA sequencing. The MIC and K earths had clay contents of 20.7% and 13.3%, respectively, and methylene blue values of 4.26 and 0.66 g/100 g, highlighting their contrasting clay reactivity. Initial cultivable fungal concentrations were approximately 3.2 log(CFU/g) in the MIC-based composite and 5.1 log(CFU/g) in the K-based composite. Despite this initial difference, both composites reached approximately 6 log(CFU/g) during the first eight days of drying, before decreasing or stabilising as gravimetric water content declined. DNA sequencing revealed shifts in microbial community composition. The two selected earths exhibited broadly similar bacterial community profiles under the tested conditions, while the communities detected in hemp shiv included taxa commonly associated with fibre degradation and retting. These results indicate an association between early fungal growth and the high moisture stage of drying, while the influence of mineralogy could not be isolated from differences in initial contamination and experimental conditions. The findings highlight the need to control the initial microbial load and drying kinetics and provide a framework for future studies combining direct water activity measurements, sterile controls and absolute microbial quantification.
SN - 2352-7102
ER -