Evaluating the Trade-offs Between Microalgal Biomass Production Rate and Nutrient Reduction in Dairy Waste Whey Permeate-amended Culture
Abstract
Leveraging microalgae for food production and aquaculture feeds utilizing waste offers an economically
efficient and circular solution to food challenges while promoting nutritional sustainability. This research
investigates the potential of whey permeate (WP), a by-product of cheese making, as a nutrient-rich
substrate for algal cultivation. The first part (Chapter 2) delves into the preparation of WP powder and
its integration into culture media, revealing that autoclaving WP with NaOH, resulting in browning
reactions, supported algal growth, especially with 1 M NaOH. Media adjustments at pH 7 optimized
biomass, and aging enhanced growth of the green alga Tetraselmis suecica, possibly due to calcium phosphate resolubilization. The solvent used with WP influenced phosphorus availability, while a light
exposure experiment explored WP degradation. The cryptophyte Chroomonas mesostigmatica had
higher growth in WP media with a headspace, emphasizing the importance of gas exchange. A second
part (Chapter 3) extends to larger-scale exploration by characterizing biomass from four algal species in
closed systems using WP as a phosphorus substitute and organic carbon source. Signs of mixotrophic
growth were observed in T. suecica and the diatom Chaetoceros muelleri, suggesting lactose assimilation
from WP. The pinguiophyte Pinguiococcus pyrenoidosus showed comparable eicosapentaenoic acid
(EPA) productivity rates in WP media during exponential phase, highlighting a promising strain for
omega-3 production. C. muelleri had significant fatty acid accumulation in stationary phase with WP
media, hinting at its suitability for biofuel production. T. suecica and C. mesostigmatica emerged as
potential candidates for protein production, and C. muelleri and C. mesostigmatica seemed suitable for
WP remediation, given their luxury uptake of phosphorus. This work lays the foundation for large-scale
production of algae-based valuable compounds using dairy waste WP as a growth substrate.