Optimizing the Production of Bacterial Cellulose Nanofibers and Nanocrystals Through Strategic Fiber Pretreatment.

Bacterial cellulose (BC) has unique properties such as high tensile strength, high crystallinity, and high purity. The fiber length of BC causes different attributes. Therefore, the degradation of BC has been studied extensively. In this study, the fibers of BC were rearranged via a DMAc-LiCl solvent and BC was degraded in the wet state. Two different degradation methods were applied: milling with liquid nitrogen and autoclave treatment. The degraded BCs were characterized by FTIR, TEM, AFM, TGA, and XRD. The solvent helps to align the fibers, making them more crystalline. The degraded BCs had a lower crystalline ratio than untreated BC, due to increased hydrogen bonding during degradation in the wet state. Degradation with an autoclave produced two different degraded BCs: nanofibrils and spherical nanocrystals, with and without solvent pretreatment, respectively. The nanofibril lengths were between 312 and 700 nm depending on the applied method, and the spherical nanocrystal size was 56 nm. The rearrangement via solvent causes an important difference in the degradation of BC. Nanofibrils and nanocrystals can be obtained, depending on the rearrangement of fibers before the degradation process.

DaimonDNA: A portable, low-cost loop-mediated isothermal amplification platform for naked-eye detection of genetically modified organisms in resource-limited settings.

The steady increase in commercialization of genetically modified organisms (GMOs) demands low-cost, rapid and portable GMO-detection methods that are technically and economically sustainable. Traditional nucleic acid detection platforms are still expensive, immobile and generate complex read-outs to be analyzed by experienced personal. Herein, we report the development of a portable, rapid and user-friendly GMO-detection biosensor, DaimonDNA. The system specifically amplifies the target DNA using loop-mediated isothermal amplification (LAMP) and provides real-time, naked-eye detection with Hydroxynaphthol blue reagent in less than 30 min. The construction of the platform relies on 3D printing and off-the-shelf electronic components that makes it extremely low-cost (<25 Euro), light weight (108 g), mobile (6 × 6 × 3 cm) and suitable for field deployment. We present the detection of the soybean lectin gene as a species control, and P35S as a transgene element found in many GMO varieties. We confirmed specificity of the DaimonDNA biosensor using" RoundUp Ready (RRS)" and MON89788 soybean genomic DNA with P35S and lectin primer sets. We characterized sensitivity of our system using 76.92, 769.2 and 7692 copies of RRS soybean genomic DNA in a non-GMO background. We benchmarked the DNA amplification and detection efficiency of our system against a thermocycling machine by quantifying the images obtained from gel electrophoresis and showed that our system is comparable to most other reported isothermal amplification techniques. This system can also be used for widespread point-of-care or field-based testing that is infrequently performed due to the lack of rapid, inexpensive, user-friendly and portable methods.

Statistical optimization of cell disruption techniques for releasing intracellular X-prolyl dipeptidyl aminopeptidase from Lactococcus lactis spp. lactis.

X-prolyl dipeptidyl aminopeptidase (PepX) is an intracellular enzyme from the Gram-positive bacterium Lactococcus lactis spp. lactis NRRL B-1821, and it has commercial importance. The objective of this study was to compare the effects of several cell disruption methods on the activity of PepX. Statistical optimization methods were performed for two cavitation methods, hydrodynamic (high-pressure homogenization) and acoustic (sonication), to determine the more appropriate disruption method. Two level factorial design (2FI), with the parameters of number of cycles and pressure, and Box-Behnken design (BBD), with the parameters of cycle, sonication time, and power, were used for the optimization of the high-pressure homogenization and sonication methods, respectively. In addition, disruption methods, consisting of lysozyme, bead milling, heat treatment, freeze-thawing, liquid nitrogen, ethylenediaminetetraacetic acid (EDTA), Triton-X, sodium dodecyl sulfate (SDS), chloroform, and antibiotics, were performed and compared with the high-pressure homogenization and sonication methods. The optimized values of high-pressure homogenization were one cycle at 130 MPa providing activity of 114.47 mU ml(-1), while sonication afforded an activity of 145.09 mU ml(-1) at 28 min with 91% power and three cycles. In conclusion, sonication was the more effective disruption method, and its optimal operation parameters were manifested for the release of intracellular enzyme from a L. lactis spp. lactis strain, which is a Gram-positive bacterium.

Improvements of tolerance to stress conditions by genetic engineering in Saccharomyces cerevisiae during ethanol production.

Saccharomyces cerevisiae, industrial yeast isolate, has been of great interest in recent years for fuel ethanol production. The ethanol yield and productivity depend on many inhibitory factors during the fermentation process such as temperature, ethanol, compounds released as the result of pretreatment procedures, and osmotic stress. An ideal strain should be able to grow under different stress conditions occurred at different fermentation steps. Development of tolerant yeast strains can be achieved by reprogramming pathways supporting the ethanol metabolism by regulating the energy balance and detoxicification processes. Complex gene interactions should be solved for an in-depth comprehension of the yeast stress tolerance mechanism. Genetic engineering as a powerful biotechnological tool is required to design new strategies for increasing the ethanol fermentation performance. Upregulation of stress tolerance genes by recombinant DNA technology can be a useful approach to overcome inhibitory situations. This review presents the application of several genetic engineering strategies to increase ethanol yield under different stress conditions including inhibitor tolerance, ethanol tolerance, thermotolerance, and osmotolerance.

Synthesis of chitosan-caffeic acid derivatives and evaluation of their antioxidant activities.

In this study, the antioxidant activities of different molecular weights (M(w)) and grafting ratios of chitosan-caffeic acid derivatives were investigated. The grafting process was achieved using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDAC) as covalent connector under different conditions such as molecular-weight of chitosan, molar ratio of chitosan and caffeic acid, reaction temperature, pH, and reaction time. The half-inhibition concentrations (IC50) of products were calculated by reduction of the 1,1-diphenyl picryl hydrazyl in the radical-scavenging assay and reduction of the Fe³+/ferricyanide complex to the ferrous form in reducing power assay. The EDAC showed maximum activity at 3-h, pH 5.0 and room temperature conditions, except high-molecular-weight chitosan in pH 2.0. The products were water-soluble in all pH and showed lower viscosity than native chitosan. The highest grafting ratio of caffeic acid was observed at 15% in low-molecular-weight chitosan. After 5% grafting of caffeic acid into chitosan, the grafting efficiency was increased by decreasing molecular-weight of chitosan at the same conditions. Caffeic acid has main role in the antioxidant activity of products. The maximum IC50 of radical-scavenging activity (0.064 mg/ml) was observed at the highest caffeic acid containing derivative. Water-soluble chitosan and caffeic acid derivatives were obtained by this study without activity loss.