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

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.