Effect of Homogenization Method and Carvacrol Content on Microstructural and Physical Properties of Chitosan-Based Films.

The use of EOs nanoemulsion to develop active edible films offers a new way to modify transport properties and to release active compounds while improving mechanical resistance, transparency, and antioxidant and antimicrobial activity. The aim of this study was to study the influence of homogenization conditions and carvacrol content on the microstructure and physical properties of edible nanoemulsified chitosan films. Film-forming emulsions (FFE) were prepared with chitosan (1.5%), Tween 80 (0.5%), and carvacrol (0.25%, 0.5%, and 1.0%); two homogenization methods were used (rotor-stator and rotor-stator followed by high-pressure homogenization). Film internal and surface microstructure was characterized by scanning electron microscopy (SEM) and film physical properties, such as mechanical, optical, and water barrier, were evaluated. Results showed that the high-pressure homogenization method promoted a significant change on film microstructure, leading to improved properties. Carvacrol droplets were smaller and homogeneously distributed in the film when 0.5% (v/v) carvacrol was incorporated (1:1 Tween 80: carvacrol ratio). As a consequence, emulsified films obtained at high pressure were less opaque, had greater elongation, and had a lower permeability to water vapor than those obtained by the rotor-stator method. Therefore, high-pressure homogenization is a good method to obtain edible emulsified films with desirable properties for food preservation.

Quorum Sensing Signaling Molecules Positively Regulate c-di-GMP Effector PelD Encoding Gene and PEL Exopolysaccharide Biosynthesis in Extremophile Bacterium Acidithiobacillus thiooxidans.

Acidithiobacillus species are fundamental players in biofilm formation by acidophile bioleaching communities. It has been previously reported that Acidithiobacillus ferrooxidans possesses a functional quorum sensing mediated by acyl-homoserine lactones (AHL), involved in biofilm formation, and AHLs naturally produced by Acidithiobacillus species also induce biofilm formation in Acidithiobacillus thiooxidans. A c-di-GMP pathway has been characterized in Acidithiobacillus species but it has been pointed out that the c-di-GMP effector PelD and pel-like operon are only present in the sulfur oxidizers such as A. thiooxidans. PEL exopolysaccharide has been recently involved in biofilm formation in this Acidithiobacillus species. Here, by comparing wild type and ΔpelD strains through mechanical analysis of biofilm-cells detachment, fluorescence microscopy and qPCR experiments, the structural role of PEL exopolysaccharide and the molecular network involved for its biosynthesis by A. thiooxidans were tackled. Besides, the effect of AHLs on PEL exopolysaccharide production was assessed. Mechanical resistance experiments indicated that the loss of PEL exopolysaccharide produces fragile A. thiooxidans biofilms. qRT-PCR analysis established that AHLs induce the transcription of pelA and pelD genes while epifluorescence microscopy studies revealed that PEL exopolysaccharide was required for the development of AHL-induced biofilms. Altogether these results reveal for the first time that AHLs positively regulate pel genes and participate in the molecular network for PEL exopolysaccharide biosynthesis by A. thiooxidans.

Somatotropic Axis Dysfunction in Non-Alcoholic Fatty Liver Disease: Beneficial Hepatic and Systemic Effects of Hormone Supplementation.

BACKGROUND: Somatotropic axis dysfunction associated with non-alcoholic fatty liver disease (NAFLD) has potential multisystemic detrimental effects. Here, we analysed the effects of growth hormone (GH) and insulin-like growth factor-1 (IGF-1) supplementation on liver histology, adipokine profile and muscle function in an NAFLD model. METHODS: C57BL/6 mice were fed with a high fat diet (HFD) for 12 weeks and were separated into three groups treated for 4 weeks with: (1) High fat diet (HFD) (n = 10); (2) HFD + GH 9 μg/g/d (n = 10); (3) HFD + IGF-1 0.02 µg/g/d (n = 9). A control group fed a chow diet was included (n = 6). Liver histology, liver triglycerides content, serum alanine aminotransferase (ALT) activity, adiponectin and leptin serum levels, in vivo muscle strength, tetanic force and muscle fibre cross-sectional area (CSA) were measured. RESULTS: HFD + GH and HFD + IGF-1 groups showed significantly lower ALT activity compared to HFD (p < 0.01). Liver triglyceride content in HFD + GH was decreased compared to HFD (p < 0.01). Histologic steatosis score was increased in HFD and HFD + GH group (p < 0.01), whereas HFD + IGF-1 presented no difference compared to the chow group (p = 0.3). HFD + GH group presented lower serum leptin and adiponectin levels compared to HFD. GH and IGF-1 supplementation therapy reverted HFD-induced reduction in muscle strength and CSA (sarcopenia). CONCLUSIONS: GH and IGF-1 supplementation induced significant improvement in liver steatosis, aminotransferases and sarcopenia in a diet-induced NAFLD model.