Comparative study on fermentation performance in the genome shuffled Candida versatilis and wild-type salt tolerant yeast strain.

BACKGROUND: The fermentation performance of a genome-shuffled strain of Candida versatilis S3-5, isolated for improved tolerance to salt, and wild-type (WT) strain were analysed. The fermentation parameters, such as growth, reducing sugar, ethanol, organic acids and volatile compounds, were detected during soy sauce fermentation process. RESULTS: The results showed that ethanol produced by the genome shuffled strain S3-5 was increasing at a faster rate and to a greater extent than WT. At the end of the fermentation, malic acid, citric acid and succinic acid formed in tricarboxylic acid cycle after S3-5 treatment elevated by 39.20%, 6.85% and 17.09% compared to WT, respectively. Moreover, flavour compounds such as phenethyl acetate, ethyl vanillate, ethyl acetate, isoamyl acetate, ethyl myristate, ethyl pentadecanoate, ethyl palmitate and phenylacetaldehyde produced by S3-5 were 2.26, 2.12, 2.87, 34.41, 6.32, 13.64, 2.23 and 78.85 times as compared to WT. CONCLUSIONS: S3-5 exhibited enhanced metabolic ability as compared to the wild-type strain, improved conversion of sugars to ethanol, metabolism of organic acid and formation of volatile compounds, especially esters, Moreover, S3-5 might be an ester-flavour type salt-tolerant yeast. © 2016 Society of Chemical Industry.

Self-propelled round-trip motion of Janus particles in static line optical tweezers.

Controlled propulsion of microparticles and micromachines in fluids could revolutionize many aspects of technology, such as biomedicine, microfluidics, micro-mechanics, optomechanics, and cell biology. We report the self-propelled cyclic round-trip motion of metallo-dielectric Janus particles in static line optical tweezers (LOT). The Janus particle is a 5 µm-diameter polystyrene sphere half-coated with 3 nanometer thick gold film. Both experiment and theory show that this cyclic translational and rotational motion is a consequence of the collective and fine action of the gold-face orientation dependent propulsion optical force, the gradient optical force, and the spontaneous symmetry breaking induced optical torque in different regions of the LOT. This study indicates a novel way to propel and manipulate the mechanical motion of microscopic motors and machines wirelessly in fluid, air, or vacuum environments using a static optical field with a smartly designed non-uniform intensity profile allowing fully controlled momentum and angular momentum exchange between light and the particle.

Effect of salt-tolerant yeast of Candida versatilis and Zygosaccharomyces rouxii on the production of biogenic amines during soy sauce fermentation.

BACKGROUND: This study aimed to enhance and improve the quality and safety of soy sauce. In the present work, the change of biogenic amines, such as histamine, tyramine, cadaverine, spermidine, was examined by the treatment of Candida versatilis and Zygosaccharomyces rouxii, and the influence of salt-tolerant yeast on biogenic amines was analysed during the whole fermentation process. RESULTS: The results showed that the content of biogenic amines was elevated after yeast treatment and the content of biogenic amines was influenced by using yeast. The dominating biogenic amine in soy sauce was tyramine. At the end of fermentation, the concentrations of biogenic amines produced by Zygosaccharomyces rouxii and Candida versatilis in the soy mash were 122.71 mg kg(-1) and 69.96 mg kg(-1) . CONCLUSIONS: The changes of biogenic amines in high-salt liquid soy mash during fermentation process indicated that a variety of biogenic amines were increased in the fermentation ageing period, which may be due to amino acid decarboxylation to form biogenic amines by yeast decarboxylase. The fermentation period of soy sauce should be longer than 5 months because biogenic amines began to decline after this time period.

Manipulation of gold nanorods with dual-optical tweezers for surface plasmon resonance control.

Gold nanorods are too tiny to be manipulated using conventional mechanical methods. In this paper, we demonstrate the trapping, transferring, positioning and patterning of gold nanorods with dual-optical tweezers. The convenient manipulations are achieved by taking advantage of the longitudinal surface plasmon resonance of gold nanorods and the anisotropic optical trapping forces formed by two linearly polarized Gaussian beams. The trapped gold nanoparticles are positioned extremely firmly and quickly on a substrate compared with randomly dispersed ones. It is observed that gold nanorods show advantages over gold nanospheres with regard to positioning speed and stability. More importantly, versatile plasmon coupling effects have been achieved in some patterned nanorods.