Multiplexing microelectrodes for dielectrophoretic manipulation and electrical impedance measurement of single particles and cells in a microfluidic device.

This work presents a microfluidic device, which was patterned with (i) microstructures for hydrodynamic capture of single particles and cells, and (ii) multiplexing microelectrodes for selective release via negative dielectrophoretic (nDEP) forces and electrical impedance measurements of immobilized samples. Computational fluid dynamics (CFD) simulations were performed to investigate the fluidic profiles within the microchannels during the hydrodynamic capture of particles and evaluate the performance of single-cell immobilization. Results showed uniform distributions of velocities and pressure differences across all eight trapping sites. The hydrodynamic net force and the nDEP force acting on a 6 µm sphere were calculated in a 3D model. Polystyrene beads with difference diameters (6, 8, and 10 µm) and budding yeast cells were employed to verify multiple functions of the microfluidic device, including reliable capture and selective nDEP-release of particles or cells and sensitive electrical impedance measurements of immobilized samples. The size of immobilized beads and the number of captured yeast cells can be discriminated by analyzing impedance signals at 1 MHz. Results also demonstrated that yeast cells can be immobilized at single-cell resolution by combining the hydrodynamic capture with impedance measurements and nDEP-release of unwanted samples. Therefore, the microfluidic device integrated with multiplexing microelectrodes potentially offers a versatile, reliable, and precise platform for single-cell analysis.

The key role of delignification in overcoming the inherent recalcitrance of Chinese fir for biorefining.

The enzymatic digestibility of softwood is hindered for its highly recalcitrant nature to enzymatic attack. In this study, the effects of dilute sulfuric acid pretreatment (DSAP), acidic sodium chlorite pretreatment (SCP), and their combined pretreatments (DSA-SCP and SC-DSAP) on Chinese fir sawdust were investigated, respectively. Results demonstrated that lignin was the most important obstacle, and digestibility increased linearly with lignin removal yield. Furthermore, the results revealed that the order of sequential pretreatment significantly affected the delignification, and hemicellulose should be removed first. Compared to SC-DSAP, DSA-SCP involving the hemicellulose-removal-first strategy exhibited higher delignification efficiency. DSA-SCP caused lignin removal of 92.3% and the enzymatic hydrolysis was high of 97.9%. Finally, a regression model with high reliability was established to quickly evaluate pretreatment process. In summary, this study highlighted the importance of delignification for saccharification of softwood and unveiled the effect of hemicellulose on delignification.

Fumaric Acid Production from Alkali-Pretreated Corncob by Fed-Batch Simultaneous Saccharification and Fermentation Combined with Separated Hydrolysis and Fermentation at High Solids Loading.

Production of fumaric acid from alkali-pretreated corncob (APC) at high solids loading was investigated using a combination of separated hydrolysis and fermentation (SHF) and fed-batch simultaneous saccharification and fermentation (SSF) by Rhizopus oryzae. Four different fermentation modes were tested to maximize fumaric acid concentration at high solids loading. The highest concentration of 41.32 g/L fumaric acid was obtained from 20 % (w/v) APC at 38 °C in the combined SHF and fed-batch SSF process, compared with 19.13 g/L fumaric acid in batch SSF alone. The results indicated that a combination of SHF and fed-batch SSF significantly improved production of fumaric acid from lignocellulose by R. oryzae than that achieved with batch SSF at high solids loading.