Aims: To study the effect of selected bacterial strains on hemp water-retting and properties of retted fibre. Methods and Results: The trials were performed in laboratory tanks. The traditional water-retting process, without inoculum addition, was compared to a process modified by inoculating water tanks with two selected pectinolytic bacteria: the anaerobic strain Clostridium sp. L1/6 and the aerobic strain Bacillus sp. ROO40B. Six different incubation times were compared. Half the fibre obtained from each tank was combed. Micromorphological analyses were performed by scanning electron microscopy on uncombed and combed fibres. Moreover, organoleptic and chemical analyses of uncombed fibres were performed. Conclusions: The inoculum, besides speeding up the process, significantly improved the fibre quality. The fibre was not damaged by mechanical hackling, thanks to the good retting level obtained by the addition of selected strains, differently to what happened with the traditionally retted fibre. The best fibre quality was obtained after 3-4 days of retting with the addition of the bacterial inoculum. Significance and Impact of the Study: Retting is the major limitation to an efficient production of high-quality hemp fibres. The water-retting process and fibre quality were substantially improved by simultaneously inoculating water tanks with two selected pectinolytic strains

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The composition and supramolecular structure of hemp primary bast fibres have been assessed using microscopy, compositional analysis, wide-angle X-ray diffractometry and CP-MAS 13 C-NMR, in order to unambiguously define some quality parameters. The main components of the fibre wall were detected by histochemical reactions and modifications occurring during the plant growth have been pointed out. Some differences in fibre lignification degree were recorded among cultivars and confirmed by means of compositional and structural analysis. As for flax and kenaf, X-ray patterns revealed semicrystalline structure of hemp cellulose. NMR spectra and their probabilistic elaboration by MaxEnt method gave further insight on the presence of paracrystalline and amorphous phases and provided an accurate evaluation of polymeric components.

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