Direct optical microalgal growth assessment using 'dip stick' microcapillary strips: A case study with Parachlorella...

Microalgal cultivation is increasingly important for industrial, agricultural, and environmental monitoring. Current methodologies for monitoring microalgal growth require periodical sampling, bulky laboratory equipment and specialized personnel. A novel 'dip-stick' micro-cultivation methodology based on fluorinated ethylene propylene microcapillary strips is herein proposed for real-time detection of microalgal growth. Cultivation of the microalgae Parachlorella kessleri in microcapillary strips, with no replacement of growing media nor physical aeration, matched the growth rate µ observed for a sparged Erlenmeyer (µ=0.37 /day) representing a > 3-fold improvement compared to an unsparged Erlenmeyer (µ=0.12 /day). Growth modelling of P. kessleri in the microcapillary strips established light intensity as a limiting growth factor. The transparency of the microcapillary strips enabled accurate and non-invasive determination of single-cell morphology and cell cycle events, which have been benchmarked against high-resolution flow cytometry. The microanalytical solution herein presented could offer a new bioanalytical solution for in-situ water management and high-throughput microalgal productivity assessment.