Quantitative tracking of the growth of individual algal cells in microdroplet compartments

Abstract

In this paper we introduce a simple droplet-based microfluidic system consisting of two separate devices to encapsulate and culture microalgae, in contrast to cultivation in bulk liquid medium. This microdroplet technology has been used to monitor the growth of individual microalgal cells in a constant environment for extended periods of time. Single cells from three species of green microalgae, (two freshwater species Chlamydomonas reinhardtii and Chlorella vulgaris, and one saline species Dunaliella tertiolecta), were encapsulated and incubated in microdroplet compartments of diameter of B80 mm, and their growth analysed over 10 days. In all cases, the doubling time of microalgae grown in microdroplets was similar to growth in bulk. The growth of C. reinhardtii in microdroplets of varying diameters and with different initial cell numbers per droplet was investigated, as well as the effect of varying medium conditions such as pH and nitrogen concentration. This methodology offers the opportunity to study characteristics over time of individual cells and colonies, as well as to screen large numbers of them.

A microfluidic perfusion platform for cultivation and screening study of motile microalgal cells

“…The doubling time was 8-9 h, which was consistent with the previous studies in bulk and droplet cultivation of Chlamydomonas wild type 12. 21 During the exponential phase, the growth rate in the microfluidic perfusion chamber seemed to be faster compared to those in the bulk phase cultivation as shown by the slopes of cell growth (supplementary material, Fig. S6) 12 and the droplet system.…”

“…It was also reported that the viability of Chlamydomonas cells in the droplet compartments or the closed chamber depended on cell density, droplet size, and the size of inoculum. 21 Possible depletion of essential nutrients and accumulation of waste products in the closed system would affect the growth of cells. However, the microfluidic perfusion chamber (volume of 1 nl) could be appropriately refreshed with a flow rate of 2-8 nl/s, and the wastes from cells were diffused out of the chamber, resulting in a better viability and productivity.…”

“…7,9,21 Severe water absorption causes a problem of significantly reducing the transmission of light into microalgal cells grown under photoautotrophic condition. In contrast, the developed microfluidic perfusion system caused no drying problem even during long-time cultivation in outdoor environment.…”

“…S6) 12 and the droplet system. 9,21 The microchambers with 30 lm height are ideal photobioreactors that can expose enough light even to full density of cell, unlike in bulk photoreactor with severe light blocking problem by self-shading. It was also reported that the viability of Chlamydomonas cells in the droplet compartments or the closed chamber depended on cell density, droplet size, and the size of inoculum.…”

An electrostatic microwell–based biochip for phytoplanktonic cell trapping

“…Scientists started to realize these methods are not sufficient to truly understand the algal cells, as the measurements assume individuals in the population of the culture behave exactly same. [10][11][12] Observation of diversity of characters and capabilities of the true population is hindered by the data acquisition. Unlike adherent cell types such as mammalian cells, living phytoplanktonic cells, especially over a long period of time, has been poorly a) Author to whom correspondence should be addressed.…”