Cellulose nanocrystals-filled poly (vinyl alcohol) nanocomposites as waterborne coating materials of NPK fertilizer with slow release and water retention properties.

Effective fertilizers management is essential for sustainable agricultural practices. One way to improve agronomic practices is by using slow-release fertilizers (SRF) that have shown interesting role in optimizing nutrients availability for plants growth. Considering the current ecological concerns, coated SRF using ecofriendly materials continue to attract great attention. In this context, novel waterborne and biodegradable coating nanocomposite formulations were elaborated from cellulose nanocrystals (CNC)-filled poly (vinyl alcohol) (PVA) for slow release NPK fertilizer with water retention property. CNC were extracted from hemp stalks using sulfuric acid hydrolysis process and their physico-chemical characteristics were investigated. CNC with various weight loadings (6, 10, 14.5 wt%) were incorporated into PVA polymer via solvent mixing method to produce viscous coating nanocomposite formulations with moderated shear viscosity. Uniform PVA@CNC coating microlayer was applied on the surface of NPK fertilizer granules in Wurster chamber of a fluidized bed dryer at controlled spraying and drying parameters. The nitrogen, phosphorus and potassium release profiles from coated NPK fertilizer were determined in water and soil. It was found that the coating materials extended the N-P-K nutrients release time from 3 days for uncoated fertilizer to 10 and 30 days for neat PVA- and CNC/PVA-coated fertilizer in soil medium, indicating the positive role of the presence of CNC in the PVA-based coatings. The morphology, coating rate and crushing strength of the as-prepared coated products were investigated in addition to their effect on water holding capacity and water retention of the soil. Enhanced crushing strength and water retention with a positive effect on the soil moisture were observed after coating NPK fertilizer, mainly with high CNC content (14.5 wt%). Therefore, these proposed nanocomposite coating materials showed a great potential for producing a new class of SRF with high nutrients use efficiency and water retention capacity, which could be beneficial to sustainable crop production.

Production of gamma-decalactone by a psychrophilic and a mesophilic strain of the yeast Rhodotorula aurantiaca.

Among 18 psychrophilic strains isolated near the Antarctic Station, the psychrophilic strain Rhodotorula aurantiaca A19 was selected for its ability of growth and gamma-decalactone production at low temperatures. The effects of temperature, initial pH, and castor oil concentration on the growth and gamma-decalactone production by a psychrophilic and a mesophilic strain of R. aurantiaca were investigated. The highest gamma-decalactone production in flasks (5.8 g/l) was obtained with the strain A19 at 14 degrees C and initial pH 7.0 in medium containing 20 g/l castor oil. On the other hand, these factors did not affect the production of gamma-decalactone by the mesophilic strain. In fermentor, a gamma-decalactone concentration of 6.6 g/l was reached with the strain A19, whereas a maximum of 0.1 g/l was obtained with the mesophilic strain. Our results suggest that the ability to synthesize gamma-decalactone is a particularity of the strain A19, since the mesophilic strain (no. 30645) produced small amounts, and the other (no. 31354) did not exhibit this property. It is, to our knowledge, the first report of gamma-decalactone production by R. aurantiaca and furthermore by a psychrophilic yeast strain. Moreover, the amount of gamma-decalactone obtained in fermentor with the strain 19 was on the order of concentrations usually described in patents.

Comparison of Yarrowia lipolytica lipase immobilization yield of entrapment, adsorption, and covalent bond techniques.

The purpose of this study was to immobilize lipase from Yarrowia lipolytica using three methods including inclusion, adsorption, and covalent bond to study enzyme leaching, storage, and catalytic properties. Sodium alginate and chitosan were the polymers selected to immobilize lipase by inclusion. The beads of each polymer were dried by freeze drying and fluidization. The results show that chitosan was more adapted to the inclusion of lipase. Even though freeze dried, bead activity was low compared to that of fluidized beads. The freeze-drying process seems to produce suitable beads for storage at 4 and 20 degrees C. The immobilization by adsorption was carried out on both celite and silica gel. Maximum immobilization yield of 76% was obtained with celite followed by 43% in silica gel. The enzyme adsorbed on the two supports exhibited greater stability at a certain temperature (50 degrees C) and in no polar solvents (Isooctane, n-heptane, and n-hexane). In addition, the lipase immobilized by covalent bond retained residual activity equitable to 70%. It was demonstrated that the enzyme immobilized by covalent bond showed greater activity (80%) after 5 months of storage.

Enhancing the antilisterial effect of Lactobacillus curvatus CWBI-B28 in pork meat and cocultures by limiting bacteriocin degradation.

This work focused on Listeria monocytogenes growth inhibition and growth rebound in raw and cooked pork meat inoculated with Lactobacillus curvatus strains. During storage of raw meat homogenates in the presence of the bacteriocin-producing strain Lactobacillus curvatus CWBI-B28wt, the Listeria monocytogenes cfu count was initially reduced to an undetectable level, but a growth rebound occurred after two weeks, coinciding with loss of 70% of the bacteriocin activity present at the end of week 2. The Listeria growth rebound was suppressed when proteolysis of bacteriocin was countered by the absence of proteases (bacteriocin addition to cooked meat) or the presence of 1% soy flour (added to provide competing substrates). Further experiments confirmed that bacteriocin is sensitive to the action of proteolytic enzymes isolated from both Lactobacillus curvatus CWBI-B28wt and the meat matrix. Bacteriocin proteolysis thus emerges as a cause of Listeria growth rebound.