초록
The objectives of this study were to evaluate bioethanol wastewater streams (thin stillage, process condensate and scrubber/dryer samples) as potential 'green' media to culture microalgae Haematococcus pluvialis, and to assess the effectiveness of ultrasound in microalgal cell disruption and astaxanthin extraction. H. pluvialis was cultured in wastewater dilutions (20-80 times) and formulations. Astaxanthin was extracted using ultrasound with cell-disrupting chemicals (acetic acid, citric acid, hydrogen peroxide and sodium hydroxide) and astaxanthin extracting solvents (acetone, ethanol and methanol) at different extraction durations (5-35min). The results demonstrated that 60 times as the optimum dilution factor of thin stillage for microalgal growth, and a formulation known as GroAst media (60% of 60 times diluted thin stillage, and 40% of process condensate) was proposed as the best media for astaxanthin production: 0.634+/-0.009mg/ml cyst density, a 10.5% improvement over standard media. Astaxanthin extraction using ultrasound intensified the process in terms of short extraction time (25min), less chemical consumption (2M NaOH), usage of GRAS solvent (methanol), high efficiency in cell disruption, high extraction yield (80.6+/-0.9%), and suitability to extract thermolabile astaxanthin.