No abstract

No abstract

This study evaluated the efficacy of the combined application of well-characterized chitosan polymer (degree of acetylation DA = 10%, degree of polymerization DPn = 90, dispersity ÐDP = 2.8) and oligomers (paCOS) (DP = 2-17) on conidia germination and mycelial growth of Fusarium graminearum, the major causal agent of Fusarium Head Blight in wheat. The polymer alone showed a higher inhibitory effect than the paCOS mixture alone, with half-maximal inhibitory concentrations (IC50) of less than 50 µg mL⁻¹ and more than 100 µg mL⁻¹, respectively. Using time-lapse microscopy, we also showed that paCOS did not affect conidia germination at 50 μg mL⁻¹, while chitosan polymer at the same concentration led to a delay in germination and in elongation of germ tubes. Scanning electron microscopy was used to observe the chitosan-induced changes in hyphal morphology. Surprisingly, the combination of chitosan polymer and paCOS led to strong synergistic effects in inhibiting conidia germination and fungal growth, as quantified by both the Abbot and Wadley equation. To our knowledge, this is the first report on a synergistic effect of a combination of chitosan polymers and oligomers, also highlighting for the first time the importance of ÐDP when studying structure-function relationships of functional biopolymers such as chitosan. The consequences of this finding for the improvement of chitosan-based antimicrobial or plant protective products are discussed. Given the economic importance of F. graminearum, this study suggests that the combination of chitosan polymer and oligomers can be used to support an efficient, sustainable plant protection strategy.

The life cycle impact assessment (LCIA) results for the Indian chitosan supply chain, as published in the article, contain an error in the BWater use^indicator. While water use during chitin and chitosan manufacturing were accounted for in the inventory analysis (167 L/kg chitin and 250 L/kg chitosan, see section 3.2 in the article), these flows were not covered in the impact assessment calculations, thus leading to an underestimate of the overall water use in the supply chain. In Table 1 and Table 2 below, we provide the corrected values for water use, for both chitin and chitosan. These tables replace the corresponding data for BWater Depletion^in Tables 17 and 18, respectively, in the supplementary material, where the detailed LCIA results are reported for the Indian supply chain.In section 4.1 of the article, the text reads: BIn water use, the water saving is higher than the water use^. Similarly, in section 5, the text reads: BThe use of shrimp shells as raw material affects the market for animal feed, resulting in a credit in many impact indicators, especially in water use, where the net result is a water saving^. In both cases, the statement that producing chitosan leads to a net overall water saving does not hold true anymore after the correction, since the induced water use in the chitosan factory is higher than the water saving associated to the raw material.Below, we provide corrected versions for Figs. 3, 4, and 7. It must be highlighted that compared to the figures in the article, only the water use indicator has been subject to corrections.The online version of the original article can be found at http://dx

Chitin is one of the most abundant biomolecules on earth, and its partially de-N-acetylated counterpart, chitosan, is one of the most promising biotechnological resources due to its diversity in structure and function. Recently, chitin and chitosan modifying enzymes (CCMEs) have gained increasing interest as tools to engineer chitosans with specific functions and reliable performance in biotechnological and biomedical applications. In a search for novel CCME, we isolated chitinolytic and chitosanolytic microorganisms from soils with more than ten-years history of chitin and chitosan exposure and screened them for chitinase and chitosanase isoenzymes as well as for their patterns of oligomeric products by incubating their secretomes with chitosan polymers. Of the 60 bacterial strains isolated, only eight were chitinolytic and/or chitosanolytic, while 20 out of 25 fungal isolates were chitinolytic and/or chitosanolytic. The bacterial isolates produced rather similar patterns of chitinolytic and chitosanolytic enzymes, while the fungal isolates produced a much broader range of different isoenzymes. Furthermore, diverse mixtures of oligosaccharides were formed when chitosan polymers were incubated with the secretomes of select fungal species. Our study indicates that soils with a history of chitin and chitosan exposure are a good source of novel CCME for chitosan bioengineering.