Microfluidic Microalgae System: A Review.

Microalgae that have recently captivated interest worldwide are a great source of renewable, sustainable and economical biofuels. The extensive potential application in the renewable energy, biopharmaceutical and nutraceutical industries have made them necessary resources for green energy. Microalgae can substitute liquid fossil fuels based on cost, renewability and environmental concern. Microfluidic-based systems outperform their competitors by executing many functions, such as sorting and analysing small volumes of samples (nanolitre to picolitre) with better sensitivities. In this review, we consider the developing uses of microfluidic technology on microalgal processes such as cell sorting, cultivation, harvesting and applications in biofuels and biosensing.

Identification of Microorganisms Using an EWOD System.

Among the advantages of an electrowetting-on-dielectric (EWOD) chip are its uncomplicated fabrication and low cost; one of its greatest strengths that might be applied in the field of biomedical technology is that it can accurately control volume and reduces the amount of samples and reagents. We present an EWOD for the biochemical identification of microorganisms, which is required to confirm the source of microbial contamination or quality inspection of product-added bacteria, etc. The traditional kit we used existed in the market; the detection results are judged by the pattern of color change after incubation. After a preliminary study, we confirmed that an image-processing tool (ImageJ) provides a suitable method of analysis, and that, when the concentration of the sugar reagent is 38 µg/µL, the best operating parameters for the EWOD chip in silicone oil are 40 V and 1.5 kHz. Additionally, we completed the biochemical identification of five bacterial species on the EWOD chip at the required concentration of the kit. Next, we found a decreased duration of reaction and that the least number of bacteria that were identifiable on the chip lies between 100 and 1000 CFU per droplet. Because the number of bacteria required on the chip is much smaller than for the kit, we tested whether a single colony can be used for identification, which provided a positive result. Finally, we designed an experimental flow to simulate an actual sample in an unclean environment, in which we divided the various processed samples into four groups to conduct experiments on the chip.

Paper-based device for separation and cultivation of single microalga.

Single-cell separation is among the most useful techniques in biochemical research, diagnosis and various industrial applications. Microalgae species have great economic importance as industrial raw materials. Microalgae species collected from environment are typically a mixed and heterogeneous population of species that must be isolated and purified for examination and further application. Conventional methods, such as serial dilution and a streaking-plate method, are intensive of labor and inefficient. We developed a paper-based device for separation and cultivation of single microalga. The fabrication was simply conducted with a common laser printer and required only a few minutes without lithographic instruments and clean-room. The driving force of the paper device was simple capillarity without a complicated pump connection that is part of most devices for microfluidics. The open-structure design of the paper device makes it operable with a common laboratory micropipette for sample transfer and manipulation with a naked eye or adaptable to a robotic system with functionality of high-throughput retrieval and analysis. The efficiency of isolating a single cell from mixed microalgae species is seven times as great as with a conventional method involving serial dilution. The paper device can serve also as an incubator for microalgae growth on simply rinsing the paper with a growth medium. Many applications such as highly expressed cell selection and various single-cell analysis would be applicable.

A multilayer concentric filter device to diminish clogging for separation of particles and microalgae based on size.

Microalgae species have great economic importance; they are a source of medicines, health foods, animal feeds, industrial pigments, cosmetic additives and biodiesel. Specific microalgae species collected from the environment must be isolated for examination and further application, but their varied size and culture conditions make their isolation using conventional methods, such as filtration, streaking plate and flow cytometric sorting, labour-intensive and costly. A separation device based on size is one of the most rapid, simple and inexpensive methods to separate microalgae, but this approach encounters major disadvantages of clogging and multiple filtration steps when the size of microalgae varies over a wide range. In this work, we propose a multilayer concentric filter device with varied pore size and is driven by a centrifugation force. The device, which includes multiple filter layers, was employed to separate a heterogeneous population of microparticles into several subpopulations by filtration in one step. A cross-flow to attenuate prospective clogging was generated by altering the rate of rotation instantly through the relative motion between the fluid and the filter according to the structural design of the device. Mixed microparticles of varied size were tested to demonstrate that clogging was significantly suppressed due to a highly efficient separation. Microalgae in a heterogeneous population collected from an environmental soil collection were separated and enriched into four subpopulations according to size in a one step filtration process. A microalgae sample contaminated with bacteria and insect eggs was also tested to prove the decontamination capability of the device.

Magnetic bead-based DNA detection with multi-layers quantum dots labeling for rapid detection of Escherichia coli O157:H7.

This work demonstrated the feasibility of detecting 250zM Escherichia coli O157:H7 eaeA target DNA by using a magnetic bead-based DNA detection assay with designed labeling strategy within 40-60min. The magnetic beads were used as the solid support for the binding probe and isolated the target DNA from the sample. The detection signals could be amplified from the multi-layers biotin-streptavidin conjugated quantum dots based on binding with specific designed biotinlyted linker. This assay method would provide a simple, rapid, and ultra-sensitive detection method for DNA or other biomolecular analysis.

Identification of Salmonella enteritidis isolates by polymerase chain reaction and multiplex polymerase chain reaction.

The polymerase chain reaction and the multiplex polymerase chain reaction were developed for detection of Salmonella and for identification of the serotype enteritidis. Three sets of primers were selected from different genomic sequences amplifying a 429 bp fragment specific for the genus Salmonella within a randomly cloned sequence, including a 250 bp fragment within the spv gene, and a 310 bp fragment within the sefA gene specific for Salmonella enteritidis. The polymerase chain reaction and the multiplex polymerase chain reaction were used for detecting S. enteritidis isolated from stool samples during outbreaks of foodborne gastroenteritis between 1992 and 1998 in Taiwan. The sefA gene was detected in all 27 strains of S. enteritidis by this polymerase chain reaction method. Multiplex polymerase chain reaction could detect 3 genes in all strains, but could not detect the spv gene in 2 strains. The sensitivity of the polymerase chain reaction and the multiplex polymerase chain reaction were 10(4) and 10(5) cells/mL, respectively. In double polymerase chain reaction, the sensitivity increased to 100 cells/mL. These data indicate that the specificity and sensitivity of the polymerase chain reaction and the multiplex polymerase chain reaction make them potentially valuable tools for diagnosis of S. enteritidis infection and that they may be used for the identification of S. enteritidis responsible for sporadic enteritis cases.