Development of antimicrobial composite materials for food packaging applications

Due to increasing environmental concerns regarding plastic waste, the development of composite film materials from biodegradable polymers and natural food additives is gaining more attention. Over the last few decades, the safety of synthetic additives that are commonly added as food additives has also been questioned because of their potential toxicity, carcinogenicity and teratogenicity effects. Natural antimicrobial agent could be a promising and versatile component in food packaging materials to improve their physiochemical, antioxidant and antimicrobial properties and hence, improve food quality and shelf life. In this study, novel chitosan/acetylated starch and polyvinyl alcohol/chitosan composite films were developed via a solution casting technique. In addition, a novel Escherichia phage, CAM-21, was isolated from a slurry lagoon at a local dairy farm before incorporating into soy protein isolate-based films. The results indicate that the chitosan/acetylated starch films incorporated with cinnamon and clove essential oils displayed enhanced light, water vapor, and oxygen barrier characteristics, as well as excellent antibacterial activity against spoilage bacteria and the pathogen, Escherichia coli O157:H7, on beef. Polyvinyl alcohol/chitosan films incorporated with aminosilane-modified bacterial nanocellulose and 4-hexylresorcinol exhibited improved mechanical, water vapor barrier, antioxidant, and antimicrobial properties against spoilage bacteria on vacuum packaged refrigerated raw beef. Also, CAM-21 has a broad host spectrum against various serotypes of Shiga toxin-producing E. coli. The growth of E. coli O157:H7 was effectively controlled in phage-treated milk, ground beef and baby spinach. Soy protein isolate films incorporated with CAM-21 showed excellent antimicrobial activity against E. coli O157:H7 in broth and refrigerated beef products. This project demonstrates the potential application of natural antimicrobial agents to produce novel composite films for antimicrobial food packaging.Includes bibliographical references

Rheological properties of cellulose nanocrystal-embedded polymer composites: a review

Nanotechnology provides useful insights into the behavioural properties of materials from the nanoscale point of view, enabling researchers to develop new materials that were previously inconceivable. Cellulose is an ideal candidate for nanomaterial for nanotechnology because of its nanofibrillar structure, abundance, renewability, biodegradability and eco-friendly nature. Nanocrystalline cellulose materials have become the focus many studies related to these materials and their applications. This review summarises the current knowledge on the field of nanomaterials, focussing mainly on the rheological behaviour of polymer nanocomposites embedded with nanocrystalline cellulose. This review will enable better understanding of the use of nanocrystalline cellulose for the development and applications of cellulose nanocrystal-based nanocomposites

A Novel Cold-Active Lipase from Candida albicans: Cloning, Expression and Characterization of the Recombinant Enzyme

A novel lipase gene lip5 from the yeast Candida albicans was cloned and sequenced. Alignment of amino acid sequences revealed that 86–34% identity exists with lipases from other Candida species. The lipase and its mutants were expressed in the yeast Pichia pastoris, where alternative codon usage caused the mistranslation of 154-Ser and 293-Ser as leucine. 154-Ser to leucine resulted in loss of expression of Lip5, and 293-Ser to leucine caused a marked reduction in the lipase activity. Lip5-DM, which has double mutations that revert 154 and 293 to serine residues, showed good lipase activity, and was overexpressed and purified by (NH4)2SO4 precipitation and ion-exchange chromatography. The pure Lip5-DM was stable at low temperatures ranging from 15–35 °C and pH 5–9, with the optimal conditions being 15–25 °C and pH 5–6. The activation energy of recombinant lipase was 8.5 Kcal/mol between 5 and 25 °C, suggesting that Lip5-DM was a cold–active lipase. Its activity was found to increase in the presence of Zn2+, but it was strongly inhibited by Fe2+, Fe3+, Hg2+ and some surfactants. In addition, the Lip5-DM could not tolerate water-miscible organic solvents. Lip5-DM exhibited a preference for the short-and medium-chain length p-nitrophenyl (C4 and C8 acyl group) esters rather than the long chain length p-nitrophenyl esters (C12, C16 and C18 acyl group) with highest activity observed with the C8 derivatives. The recombinant enzyme displayed activity toward triacylglycerols, such as olive oil and safflower oil

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe

Retrospective evaluation of whole exome and genome mutation calls in 746 cancer samples

Funder: NCI U24CA211006Abstract: The Cancer Genome Atlas (TCGA) and International Cancer Genome Consortium (ICGC) curated consensus somatic mutation calls using whole exome sequencing (WES) and whole genome sequencing (WGS), respectively. Here, as part of the ICGC/TCGA Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium, which aggregated whole genome sequencing data from 2,658 cancers across 38 tumour types, we compare WES and WGS side-by-side from 746 TCGA samples, finding that ~80% of mutations overlap in covered exonic regions. We estimate that low variant allele fraction (VAF < 15%) and clonal heterogeneity contribute up to 68% of private WGS mutations and 71% of private WES mutations. We observe that ~30% of private WGS mutations trace to mutations identified by a single variant caller in WES consensus efforts. WGS captures both ~50% more variation in exonic regions and un-observed mutations in loci with variable GC-content. Together, our analysis highlights technological divergences between two reproducible somatic variant detection efforts

Preparation and characterization of polyvinyl alcohol/chitosan composite films reinforced with cellulose nanofiber / Choo Kai Wen

Natural nanocellulose reinforced polymer composites are recently gaining interest in various applications. Much more attentions have been focused to replace petroleum-derived polymers with sustainable natural biopolymers due to their unique properties. In many instances, the fabrication of composites through blending approach of natural and synthetic polymers does not meet the satisfaction on their properties. Thus, the reinforcement of nanofiller into the composite could be a promising way to produce biomaterials with desired properties. The purpose of this project is to discover the effect of cellulose nanofiber (CNF) reinforced on the characteristics of polyvinyl alcohol (PVA)/chitosan (CS) composite. In this study, microcrystalline cellulose (MCC) was oxidized by 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidation method. Bio-nanocomposite films were then prepared from PVA/CS polymeric blends with different TEMPO-mediated oxidized cellulose nanofiber (TOCN) contents (0, 0.5, 1.0 and 1.5 wt%) via the solution casting method. The composite films were characterized in terms of crystallinity, morphological, mechanical, chemical and thermal properties. The morphology results from field emission scanning electron microscopy (FESEM) analysis justified that homogenous dispersion of TOCNs was achieved up to 1.0 wt% in the PVA/CS composite. For the tensile profile of pure PVA/CS composite, it was observed that the optimum tensile strength and elongation at break has been achieved in PVA/CS/TOCNs = 75/25/0.5 composite. For the thermal study by thermogravimetric analysis (TGA) and differential thermogravimetric (DTG) analysis, there was improvement of 4°C and 6°C in onset temperature and maximum degradation temperature, respectively when 1.0 wt% of TOCNs was added into the PVA/CS = 50/50 composite. As evidenced by Fourier transform infrared (FTIR) analysis, itshowed the well interaction between the functional groups of TOCNs and PVA/CS composite matrix due to strong hydrogen bonding. Based on the crystallinity study by x-ray diffraction (XRD), the addition of TOCNs has successfully enhanced the molecular ordering in the amorphous phase of the composite. Hence, the improved characteristics of TOCNs reinforced composites could be strongly beneficial in numerous applications in the future. Keywords: bio-nanocomposite films, polyvinyl alcohol, chitosan, TEMPO-oxidized cellulose nanofiber, solution casting

Retrospective evaluation of whole exome and genome mutation calls in 746 cancer samples

The Cancer Genome Atlas (TCGA) and International Cancer Genome Consortium (ICGC) curated consensus somatic mutation calls using whole exome sequencing (WES) and whole genome sequencing (WGS), respectively. Here, as part of the ICGC/TCGA Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium, which aggregated whole genome sequencing data from 2,658 cancers across 38 tumour types, we compare WES and WGS side-by-side from 746 TCGA samples, finding that ~80% of mutations overlap in covered exonic regions. We estimate that low variant allele fraction (VAF < 15%) and clonal heterogeneity contribute up to 68% of private WGS mutations and 71% of private WES mutations. We observe that ~30% of private WGS mutations trace to mutations identified by a single variant caller in WES consensus efforts. WGS captures both ~50% more variation in exonic regions and un-observed mutations in loci with variable GC-content. Together, our analysis highlights technological divergences between two reproducible somatic variant detection efforts.The Cancer Genome Atlas (TCGA) and International Cancer Genome Consortium (ICGC) curated consensus somatic mutation calls using whole exome sequencing (WES) and whole genome sequencing (WGS), respectively. Here, as part of the ICGC/TCGA Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium, which aggregated whole genome sequencing data from 2,658 cancers across 38 tumour types, we compare WES and WGS side-by-side from 746 TCGA samples, finding that -80% of mutations overlap in covered exonic regions. We estimate that low variant allele fraction (VAFPeer reviewe

Retrospective evaluation of whole exome and genome mutation calls in 746 cancer samples

Funder: NCI U24CA211006Abstract: The Cancer Genome Atlas (TCGA) and International Cancer Genome Consortium (ICGC) curated consensus somatic mutation calls using whole exome sequencing (WES) and whole genome sequencing (WGS), respectively. Here, as part of the ICGC/TCGA Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium, which aggregated whole genome sequencing data from 2,658 cancers across 38 tumour types, we compare WES and WGS side-by-side from 746 TCGA samples, finding that ~80% of mutations overlap in covered exonic regions. We estimate that low variant allele fraction (VAF < 15%) and clonal heterogeneity contribute up to 68% of private WGS mutations and 71% of private WES mutations. We observe that ~30% of private WGS mutations trace to mutations identified by a single variant caller in WES consensus efforts. WGS captures both ~50% more variation in exonic regions and un-observed mutations in loci with variable GC-content. Together, our analysis highlights technological divergences between two reproducible somatic variant detection efforts