Ectoine production by Alkalibacillus haloalkaliphilus-Bioprocess development using response surface methodology and model-driven strategies

Halophile microorganisms are important ectoine producers and are applied in industrial applications. The growth and osmoregulation are distinguished based on the diversity of environmental distribution and require holistic investigations of cultivation condition and osmotic response. The barely investigated halophilic bacterium Alkalibacillus haloalkaliphilus is able to accumulate the compatible solute ectoine, while growing under environmental stress conditions. Since microbial growth and ectoine production are functions of the process key parameters such as salinity, pH value, and temperature, the optimization resulted in three significant process strategies that were estimated by response surface methodology. For each strategy, single-cell analysis was performed using a newly developed staining method for monitoring the membrane potential of halophilic microorganisms directly in the cultivation medium. The flow cytometric method was shown to reveal the physiological state during ectoine production and has a great potential to be applied for basic research, process optimization, and quality control.