A microfluidic photobioreactor for simultaneous observation and cultivation of single microalgal cells or cell aggregates

Abstract

Microalgae are an ubiquitous and powerful driver of geochemical cycles which have formed Earth’s biosphere since early in the evolution. Lately, microalgal research has been strongly stimulated by economic potential expected in biofuels, wastewater treatment, and high-value products. Similar to bacteria and other microorganisms, most work so far has been performed on the level of suspensions which typically contain millions of algal cells per millilitre. The thus obtained macroscopic parameters average cells, which may be in various phases of their cell cycle or even, in the case of microbial consortia, cells of different species. This averaging may obscure essential features which may be needed for the correct understanding and interpretation of investigated processes. In contrast to these conventional macroscopic cultivation and measuring tools, microfluidic single-cell cultivation systems represent an excellent alternative to study individual cells or a small number of mutually interacting cells in a well-defined environment. A novel microfluidic photobioreactor was developed and successfully tested by the photoautotrophic cultivation of Chlorella sorokiniana . The reported microbioreactor facilitates automated long-term cultivation of algae with controlled temperature and with an illumination adjustable over a wide range of photon flux densities. Chemical composition of the medium in the microbioreactor can be stabilised or modulated rapidly to study the response of individual cells. Furthermore, the algae are cultivated in one focal plane and separate chambers, enabling single-cell level investigation of over 100 microcolonies in parallel. The developed platform can be used for systematic growth studies, medium screening, species interaction studies, and the thorough investigation of light-dependent growth kinetics.

Microfluidics for microalgal biotechnology

“…Many of the microfluidic‐based systems were improved for long‐term cultivation and imaging of microalgal cells simultaneously. These systems/approaches have great potential to elucidate cell activities like photosynthesis, cellular development and behavioral differences of microalgae (Luke et al, 2016; Wang et al, 2016; Y. Wang, Wang, et al, 2019; Westerwalbesloh et al, 2019). For example, the intensity of chlorophyll fluorescence of a single microalgal cell can be measured by fluorescence detection systems integrated with microfluidics.…”

“…It was observed that, after sorting by RADS, 92.7% of the cells were viable(Wang et al, 2017). Evaluating the results of Raman spectroscopy (chemical composition) and LIBS (basic composition) measurements together provide a more accurate selection and environmental impact assay with complete biochemical composition of algal biomass(Pořízka et al, 2012;Pořízka et al, 2014).2.2 | CultivationMany of the microfluidic-based systems were improved for longterm cultivation and imaging of microalgal cells simultaneously.These systems/approaches have great potential to elucidate cell activities like photosynthesis, cellular development and behavioral differences of microalgae(Luke et al, 2016;Wang et al, 2016;Westerwalbesloh et al, 2019). For example, the intensity of chlorophyll fluorescence of a single microalgal cell can be measured by fluorescence detection systems integrated with microfluidics.…”

Bottom-illuminated orbital shaker for microalgae cultivation

“…In laboratory conditions, microalgae are grown using dedicated instruments in growth media, which provide the nutrients and water [2] , [3] . These instruments vary in size between microfluidic [4] , [5] and industrial scale implementations [3] , [6] . Their purpose is to agitate and illuminate the cultures.…”

Microfluidic and mathematical modeling of aquatic microbial communities

“…In these three platforms, a co-culture can be easily realized via the introduction of pre-mixed microbes. Microtraps have been designed to trap algal cells using size restriction with the dimension of the trap size in the order of a few micrometers for cell growth study [20][21][22]. This method works well with a monolayer of trapped cells perfused with media through connected channels, and have been used successfully in studies of synthetic bacteria co-cultures [23,24].…”