Preparation and characterization of Paraloid B-72/TiO2 nanocomposite and their effect on the properties of polylactic acid as strawberry coating agents

In this study, Paraloid B-72 (poly methyl methacrlylate/ethylacrylate 70:30) and its nanocomposites with titanium dioxide (TiO₂) concentration 1–5% have been prepared by emulsion polymerization technique and characterized by transmission electron microscope (TEM), Fourier-transform infrared spectroscopy (FT-IR) in addition to antimicrobial activity against Aspergillus niger and Penicillium sp. The prepared Paraloid B-72 and its titanium dioxide nanocomposites was grafted onto polylactic acid (PLA) and the results indicate that the grafting percentage reached to maximum value using the nanocomposite of Paraloid B-72 with 3% TiO₂. PLA grafted with Paraloid B-72/3% TiO₂ has been characterized by scanning electron microscope (SEM), FT-IR as well as mechanical and color change measurements. The results show that incorporation of Paraloid B-72 / TiO₂ improved the properties of PLA. The produced PLA grafted Paraloid B-72 and its 5% titanium dioxide have been used for coating strawberry to enhance and control the cold storage at 4°C for 15 days.     

Nisin as a Food Preservative: Part 2: Antimicrobial Polymer Materials Containing Nisin

Nisin is the only bacteriocin approved as a food preservative because of its antibacterial effectiveness and its negligible toxicity for humans. Typical problems encountered when nisin is directly added to foods are mainly fat adsorption leading to activity loss, heterogeneous distribution in the food matrix, inactivation by proteolytic enzymes, and emergence of resistance in normally sensitive bacteria strains. To overcome these problems, nisin can be immobilized in solid matrices that must act as diffusional barriers and allow controlling its release rate. This strategy allows maintaining a just sufficient nisin concentration at the food surface. The design of such antimicrobial materials must consider both bacterial growth kinetics but also nisin release kinetics. In this review, nisin incorporation in polymer-based materials will be discussed and special emphasis will be on the applications and properties of antimicrobial food packaging containing this bacteriocin.     

Cloning and identification of HEM14, the yeast gene for mitochondrial protoporphyrinogen oxidase

A respiratory-defective mutant (C54) of Saccharomyces cerevisiae was found to have a phenotype consistent with a mutation in either mitochondrial protoporphyrinogen oxidase or ferrochelatase. The mutant is grossly deficient in hemes, accumulates protoporphyrin and is rescued by exogenous heme. The increased levels of protoporphyrin at the expense of heme is indicative of a block in one of the two last steps of the heme biosynthetic pathway. Complementation of C54 by a known ferrochelatase mutant suggested that the defect was most likely in HEM14 encoding protoporphyrinogen oxidase. A plasmid capable of complementing C54 was obtained by transformation with a yeast genomic plasmid library. A partial sequence of the insert identified the gene as reading frame YER014 of yeast chromosome V (GenBank Accession Number U18778). This reading frame codes for a protein homologous to human protoporphyrinogen oxidase. Disruption of this gene elicits a respiratory defect and accumulation of protoporphyrin. The phenotype of the null mutant together with the homology of YER014p to human protoporphyrinogen oxidase provide compelling evidence that YER014 is HEM14.     

Lipocalin 2 Influences Bone and Muscle Phenotype in the MDX Mouse Model of Duchenne Muscular Dystrophy

Lipocalin 2 (Lcn2) is an adipokine involved in bone and energy metabolism. Its serum levels correlate with bone mechanical unloading and inflammation, two conditions representing hallmarks of Duchenne Muscular Dystrophy (DMD). Therefore, we investigated the role of Lcn2 in bone loss induced by muscle failure in the MDX mouse model of DMD. We found increased Lcn2 serum levels in MDX mice at 1, 3, 6, and 12 months of age. Consistently, Lcn2 mRNA was higher in MDX versus WT muscles. Immunohistochemistry showed Lcn2 expression in mononuclear cells between muscle fibres and in muscle fibres, thus confirming the gene expression results. We then ablated Lcn2 in MDX mice, breeding them with Lcn2^−/− mice (MDXxLcn2^−/−), resulting in a higher percentage of trabecular volume/total tissue volume compared to MDX mice, likely due to reduced bone resorption. Moreover, MDXxLcn2^−/− mice presented with higher grip strength, increased intact muscle fibres, and reduced serum creatine kinase levels compared to MDX. Consistently, blocking Lcn2 by treating 2-month-old MDX mice with an anti-Lcn2 monoclonal antibody (Lcn2Ab) increased trabecular volume, while reducing osteoclast surface/bone surface compared to MDX mice treated with irrelevant IgG. Grip force was also increased, and diaphragm fibrosis was reduced by the Lcn2Ab. These results suggest that Lcn2 could be a possible therapeutic target to treat DMD-induced bone loss.     

Physicochemical Properties of Jacatupé (Pachyrhizus erosus L. Urban) Starch

The physicochemical properties of the starch extracted from Jacatupé (Pachyrhizus erosus L. Urban) were studied. The small-sized granules (approximately <10μm long) present varying geometric forms: round, cupoliform and convex-biconcave shaped granules predominate. The amylose content is 23% and crystallinity pattern is type A. Values for intrinsic viscosity and absolute density are similar to those for cassava (Manihot utilissima) starch. Extraction and purification procedures are easy to perform. Root productivity is high (50t/hectare). According to these results, Jacatupé roots can be considered a new alternative source for starch production.