Modeling the Retting of Linseed Straw with Controlled Humidification and Consideration of the Microbiota Composition

The aim of this study was to investigate the patterns governing the conversion of oilseed flax straw into retted straw under the climatic conditions of southern Ukraine through examining moisture absorption, moisture desorption, and the associated microbiological processes. It was established that stem moisture content approaching 100% is reached within 10 min of moistening, after which the process shifts from adsorption of free water to absorption of bound water. Analysis of the moisture desorption curves demonstrated that a single moistening event is insufficient to sustain the moisture level required for active microbial proliferation, as moisture content decreases by approximately 45% within the first hour and gradually reverts to baseline values thereafter. The mathematical modeling results indicate that without supplementary moistening, the biological conversion of straw into retted straw is virtually negligible. It was found that twice-daily moistening promotes the dominance of pectinolytic microorganisms, ensuring efficient breakdown of pectic substances and the formation of high-quality retted straw. However, after 5–6 days of retting, a sharp increase in the numbers of cellulolytic and pathogenic microflora is observed, which may lead to degradation of the cellulose complex and deterioration of fiber properties. The obtained findings can be used to optimize bast biomass processing technologies, develop predictive systems for the retting process, and improve the quality of the resulting fiber.