Perfusion Microfermentor Integrated into a Fiber Optic Quasi-Elastic Light Scattering Sensor for Fast Screening of Microbial Growth Parameters

Abstract

This research presents a microfermentor integrated into an optical fiber sensor based on quasi-elastic light scattering (QELS) to monitor and swiftly identify cellular growth kinetic parameters. The system uses a 1310 nm laser light that is guided through single-mode silica optical fibers to the interior of perfusion chambers, which are separated by polycarbonate membranes (470 nm pores) from microchannels, where a culture medium flows in a constant concentration. The system contains four layers, a superior and an inferior layer made of glass, and two intermediate poly(dimethylsiloxane) layers that contain the microchannels and the perfusion chambers, forming a reversible microfluidic device that requires only the sealing of the fibers to the inferior glass cover. The QELS autocorrelation decay rates of the optical signals were correlated to the cells counting in a microscope, and the application of this microsystem to the monitoring of alcoholic fermentation of Saccharomyces cerevisiae resulted in the kinetic parameters of KM = 4.1 g/L and μm = 0.49 h−1. These results agree with both the data reported in the literature and with the control batch test, showing that it is a reliable and efficient biological monitoring system.

Evaluation of Silica Nanofluids in Static and Dynamic Conditions by an Optical Fiber Sensor

“…The OFS is depicted in Figure 2 [29]. Light emitted by a 1310 nm laser diode is launched into the standard silica single-mode fiber (SMF).…”

“…Consequently, one may evaluate ln(G1) to retrieve Γm, and then investigate particle concentration and flow velocity. The optical signal is acquired at 1 kHz sampling rate and processed by MATLAB (Mathworks) routines [29]. To create an environment with different particles concentrations (suitable for the simulation of concentration disturbances), two (1000 mL)-test tubes were filled with silica suspensions of 1 wt% of concentration.…”

Use of Optical Fiber Sensor for Monitoring the Degradation of Ac-Dex Biopolymeric Nanoparticles

“…The sensor is calibrated for collecting 20,000 intensity measurements at 1 kHz rate. Finally, the acquired signals are processed by routines developed in MATLAB [6].…”

“…The full setup presenting the electronics, the analysis of an Ac-Dex suspension and the scattering of the light is shown in Figure 2. Then, a suspension of Ac-Dex DE (initial concentration of 4 mg/mL) was continuously analyzed over 12 h for evaluating its degradation under mildly acidic pH (5.5 buffer): as the colloidal particles are disassembled, the decrease of Γm value is expected [6]. All the colloidal suspensions used in the experiments were kept in an ultrasound temperature-controlled bath (5.9L Ultrasound Bath, Ultronique Eco-Sonics, Indaiatuba, SP, Brazil) under 37 °C for simulating conditions similar to tumoral tissues [8].…”

“…In this work, colloidal dispersions of Ac-Dex were synthesized by two different routes, the single-emulsion (o/w) and the double-emulsion (w/o/w), referred as Ac-Dex SE and Ac-Dex DE, respectively. Scanning electron microscopy (SEM) was employed to investigate the morphology of Ac-Dex nanoparticles synthesized through these two methodologies and an optical fiber sensor [6,7] was employed to assess the colloidal behavior of Ac-Dex NPs over time. More specifically, the stability of a colloidal set was investigated during 12 h in an acidic environment (pH 5.5) under 37 °C, which corresponds to the cancer tissue conditions.…”