Thymol-Loaded Polymeric Nanoparticles Improve the Postharvest Microbiological Safety of Blueberries.

Research background: The presence of Yersinia enterocolitica on raw food products raises the concern of yersiniosis as most of the berries are consumed raw. This is a challenging issue from the food safety aspect since it could increase the occurrence of foodborne diseases among humans. Thus, it is crucial to implement an effective sanitation before the packaging. Experimental approach: This study aims to synthesize and characterize thymol-loaded polyvinyl alcohol (Thy/PVA) nanoparticles as a sanitizer for postharvest treatment of blueberries. Thy/PVA nanoparticles were characterized by spectroscopic and microscopic approaches, prior to the analyses of antimicrobial properties. Results and conclusions: The diameter size of the nanoparticles was on average 84.7 nm, with a surface charge of -11.73 mV. Based on Fourier transform infrared (FTIR) measurement, the Thy/PVA nanoparticles notably shifted to the frequency of 3275.70, 2869.66, 1651.02 and 1090.52 cm-1. A rapid burst was observed in the first hour of release study, and 74.9 % thymol was released from the PVA nanoparticles. The largest inhibition zone was displayed by methicillin-resistant Staphylococcus aureus (MRSA), followed by Y. enterocolitica and Salmonella typhi. However, amongst these bacteria, the inhibition and killing of Y. enterocolitica required a lower concentration of Thy/PVA nanoparticles. The treatment successfully reduced the bacterial load of Y. enterocolitica on blueberries by 100 %. Novelty and scientific contribution: Thymol is a plant-based chemical without reported adverse effects to humans. In this study, by using the nanotechnology method of encapsulation with PVA, we improved the stability and physicochemical properties of thymol. This nanoparticle-based sanitizer could potentially promote the postharvest microbiological safety of raw berries, which may become an alternative practice of food safety.

2-Octylcyclopentanone Inhibits Beta Lactam Resistant Diabetic Wound Pathogens.

Microbial infection is a frequent complication of diabetic foot ulcers, with up to 82% of ulcers being infected at the initial stage of diabetes. Furthermore, the emergence of beta lactam resistant pathogens managed to eliminate the use of beta lactam antibiotics as a chemotherapeutic alternative. This further increases the amputation and mortality rate. Hence, the aim of this study is to evaluate antimicrobial efficacy of a ketone derivative 2-octylcyclopentanone against diabetic wound pathogens. The inhibitory activity of the compound was determined using disc diffusion and broth microdilution assay. Generally, 2-octylcyclopentanone showed broad-spectrum antimicrobial activity, particularly against beta lactam resistant pathogens. The compound showed comparably better antimicrobial activity than all reference antibiotics, including chloramphenicol, streptomycin, ampicillin and penicillin. In addition, the same compound also inhibits a clinically isolated Pseudonomas aeruginosa that was resistant to all reference antibiotics. The activity was microbicidal based on the low minimal lethality concentration recorded, particularly on MRSA, P. aeruginosa and Candida utilis. The killing efficiency of the compound was concentration dependent. During kill curve analysis, the inhibitory activity of 2-octylcyclopentanone was concentration and time-dependent. 99.9% of reduction of bacterial growth was observed. MRSA and P. aeruginosa, two significant diabetic wound infections, are totally inhibited by the molecule at a concentration of minimum lethality concentration. In short, 2-octylcyclopentanone exhibited significant inhibitory towards wide range of diabetic wound pathogens. Which is considered crucial since it will provide a safe and effective alternative treatment for diabetic ulcer infection.

Jangkitan mikrob adalah komplikasi ulser yang kerap dijangkiti pada kaki pesakit diabetes, yang boleh mencapai sehingga 82% jangkitan pada peringkat awal diabetes. Kemunculan patogen tahan beta laktam berjaya menghapuskan penggunaan antibiotik beta laktam sebagai alternatif kemoterapi. Ini meningkatkan lagi kadar amputasi dan kematian. Oleh itu, tujuan kajian ini adalah untuk menilai keberkesanan antimikrob bagi derivatif keton 2-octylcyclopentanone terhadap patogen luka diabetes. Aktiviti perencatan sebatian ditentukan menggunakan resapan cakera dan ujian cerakinan mikrodilusi. Secara amnya, 2-octylcyclopentanone menunjukkan aktiviti antimikrob spektrum luas, terutamanya terhadap patogen tahan beta laktam. Kompaun tersebut menunjukkan aktiviti antimikrob yang lebih baik berbanding semua antibiotik rujukan, termasuk kloramfenikol, streptomisin, ampisilin dan penisilin. Di samping itu, sebatian yang sama juga menghalang Pseudonomas aeruginosa yang diasingkan secara klinikal yang tahan terhadap semua antibiotik rujukan. Aktiviti ini adalah mikrobisida berdasarkan kepekatan kematian minimum yang rendah yang direkodkan, terutamanya pada MRSA, P. aeruginosa dan Candida utilis. Kecekapan membunuh kompaun adalah bergantung kepada kepekatan. Semasa analisis keluk bunuh, aktiviti perencatan 2-octylcyclopentanone adalah kepekatan dan bergantung kepada masa. 99.9% pengurangan pertumbuhan bakteria diperhatikan. MRSA dan P. aeruginosa, dua jangkitan luka diabetes yang ketara, dihalang sepenuhnya oleh molekul pada kepekatan kepekatan maut minimum. Ringkasnya, 2-octylcyclopentanone menunjukkan perencatan yang ketara terhadap pelbagai patogen luka diabetes. Yang dianggap penting kerana ia akan menyediakan rawatan alternatif yang selamat dan berkesan untuk jangkitan ulser diabetik.

Naringenin-Grafted Polyvinyl Alcohol (Na/PVA) Nanoparticles: Synthesis, Characterisation and In Vitro Evaluation of Its Antimicrobial Efficiency on Fresh Beef.

Food preservatives are commonly used to guarantee the safety and quality of food. Naturally-derived preservatives are preferred by the consumers as chemical preservatives are associated with adverse side effects. The application of naringenin as a food preservative is restricted due to its high volatility, albeit known for its good efficacy in inhibiting microbial growth on food. Thus, this study aimed to synthesis and characterise naringenin-grafted PVA (Na/PVA) nanoparticles as potential meat preservative. The nano-size of naringenin was characterised by transmission electron microscopy. Finally, the antibacterial efficiency of Na/PVA nanoparticles substance was evaluated on disc diffusion assay, broth microdilution assay and using fresh beef as food model. The naringenin nanoparticles appeared in globule and smooth structure, with an average size of less than 200 nm. In total, 11.08% of naringenin nanoparticles was successfully encapsulated into PVA nanoparticles. Based on Fourier transform infrared spectra, naringenin was successfully encapsulated into PVA nanoparticles. The release of naringenin from Na/PVA nanoparticles was slow and gradual, with an initial burst release effect observed. The property was ideal for application in food model. It gained a plateau at 48 h. The Na/PVA nanoparticles depicted its antibacterial efficiency on all the test foodborne bacteria, except E. coli. It was represented by the presence of inhibition zones, which were ranged from 10 mm to 14 mm. The activity was concentration-dependent, and a higher concentration of nanoparticles was needed to kill the test bacteria. The meat coated with Na/PVA nanoparticles displayed a 100% reduction in bacterial load, where no bacterial growth was detected at the sample throughout the incubation period. The coating of nanoparticles also improved the organoleptic property of fresh beef, by maintain the meat colour. The developed nanoparticles can be potentially used nano-preservative to maintain the microbiological quality of fresh beef.

Pengawet makanan biasanya digunakan untuk menjamin keselamatan dan kualiti makanan. Pengawet semulajadi yang diperoleh ialah pilihan oleh pengguna kerana pengawet kimia dikaitkan dengan kesan sampingan yang buruk. Penggunaan naringenin sebagai pengawet makanan adalah terhad kerana turun naik yang tinggi, walaupun dikenali kerana keberkesanan yang baik dalam menghalang pertumbuhan mikrob pada makanan. Oleh itu, kajian ini bertujuan untuk mensintesis dan mencirikan nanozarah PVA (Na/PVA) naringenin sebagai pengawet daging yang berpotensi. Saiz nano naringenin dicirikan oleh mikroskopi elektron penghantaran. Akhirnya, kecekapan antibakteria bahan nanozarah Na/PVA dinilai pada disc diffusion assay, broth microdilution assay dan menggunakan daging lembu segar sebagai model kajian. Naringenin nanozarah muncul dalam globul dan struktur licin, dengan saiz purata kurang daripada 200 nm. Secara keseluruhan, 11.08% daripada naringenin nanozarah telah berjaya dimasukkan ke dalam nanozarah PVA. Berdasarkan pengubah spektra inframerah Fourier, naringenin berjaya dikapsulkan dalam nanozarah PVA. Pelepasan naringenin dari Na/PVA nanozarah adalah perlahan dan beransur-ansur, dengan kesan pelepasan mendadak diperhatikan pada fasa awal kajian. Sifat ini sesuai digunakan untuk menghalang pertumbuhan mikrob pada makanan. Ia mendapat dataran tinggi pada 48 h. Nanozarah Na/PVA menggambarkan kecekapan antibakteria pada semua bakteria bawaan makanan ujian, kecuali E. coli. Ia diwakili oleh kehadiran zon perencatan, yang berkisar dari 10 mm hingga 14 mm. Aktiviti ini bergantung kepada kepekatan, dan kepekatan nanozarah yang lebih tinggi diperlukan untuk membunuh bakteria ujian. Daging yang disalut dengan Na/PVA nanozarah menunjukkan pengurangan 100% dalam beban bakteria, di mana tiada pertumbuhan bakteria dikesan pada sampel sepanjang tempoh inkubasi. Lapisan nanozarah juga meningkatkan sifat organoleptik daging lembu segar, dengan mengekalkan warna daging. Nanozarah yang dibangunkan berpotensi digunakan nano-pengawet untuk mengekalkan kualiti mikrobiologi daging lembu segar.

Purification and physicochemical characterisation of Aspergillus niger USM F4 β-mannanase

Aims@#This present study focused on purification of fungal β-mannanase produced by Aspergillus niger USM F4 and also physicochemical characterisation of the purified enzyme.@*Methodology and results@#The purified β-mannanase with a molecular mass of ~47.4 kDa was demonstrated on SDSPAGE gel. The enzyme signified a purification degree of 4-fold, with final specific activity of 196.42 U/mg. It reached an optimum catalytic activity at pH 4.0 and 60 °C. The thermal stability of the enzyme was up to 70 °C and maintained the 50% activity after 30 min at 80 °C. Meanwhile, the pH stability was in the range of pH 3.0-9.0 and a 30 min half-life at pH 10.0. All chemical substances manifested an inhibitory effect on purified β-mannanase, with SDS (28.16 ± 0.05% residual activity) as the strongest inhibitor, followed by cupric ion (Cu2+) (49.51 ± 0.09% residual activity). As a whole, the enzyme displayed a substrate specificity in the order of locust bean gum (LBG) > carboxymethylcellulose > soluble starch > xylan from oat spelt > α-cellulose. Its preference for LBG has generated the Km and Vmax values of 0.20 mg/mL and 9.82 U/mL, respectively.@*Conclusion, significance and impact of study@#The outcomes of our study offer potential for use at industrial scales, particularly in the oligosaccharides production that involve acid-related activity, wide-ranging temperature and pH stability.