Real-time automation and monitoring of the batch growth of microalga Tetraselmis viridis and cyanobacterium Limnospira platensis

Abstract

An automated system for the real-time measurement and control of the optical density of the microalga Tetraselmis viridis and cyanobacterium Limnospira platensis has been developed based on the open-source Arduino Nano electronics platform. The system consists of a main unit, an optical density sensor, a relay unit, a temperature sensor, and associated software. The optical density sensor consists of light diodes (with a maximum emission spectrum in the infrared region at 940 nm) as a light source and photodiodes as receivers; the culture density is estimated based on the attenuation of radiation passing through it. The proposed method exhibited high accuracy (R² = 0.995, with root mean square error being approximately 0.1 g L⁻¹) in a wide range of biomass concentrations, from 0.27 to 0.97 g L⁻¹ for T. viridis and from 0.035 to 1.25 g L⁻¹ for L. platensis. The registered biomass productivity at the linear stage of batch cultivation reached 0.15 g L⁻¹ day⁻¹ for T. viridis and 0.17 g L⁻¹ day⁻¹ for L. platensis. The sensor readings were found to be dependent on air temperature, with a coefficient of 0.0136 V/°C. This suggests that the system has the potential for use in a changing outdoor environment, provided that temperature correction is applied during calculations. Furthermore, the measuring system does not require sampling from the photobioreactor or dilution of high cell concentrations prior to measuring dense microalgae cultures. This eliminates the risk of dilution error and contamination. The experimental application of the system for the studied species demonstrated its potential for use with microalgae species exhibiting diverse pigment compositions, including those prone to sedimentation and filamentous forms.

Keywords

Automatization / Optical density sensor / Microalgae / Tetraselmis / Limnospira / Arduino nano

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Funding

A.O. Kovalevsky Institute of Biology of the Southern Seas(124021300070-2)

RIGHTS & PERMISSIONS

Jiangnan University