Whey permeate as a phosphorus source for algal cultivation.

Microalgal cultivation for biodiesel and feed requires recycled nutrient resources for a sustainable long-term operation. Whey permeate (WP) from dairy processing contains high organic load (lactose, oils, and proteins) and nitrogen (resources tested for microalgal cultivation) and organic phosphorus (P) that has not yet been tested as a P source for microalgal cultivation. We explored the potential of green algae strains (brackish) and polyculture (freshwater) in exploiting P from WP added to a medium based on either seawater (7 psu) or landfill leachate. Both strains showed a capacity of using organic P in WP with equal growth rates (0.94-1.12 d-1 ) compared with chemical phosphate treatments (0.88-1.07 d-1 ). The polyculture had comparable growth rate (0.25-0.57 d-1 ) and biomass yield (152.1-357.5 mg L-1 ) and similar or higher nutrient removal rate in the leachate-WP medium (1.3-6.4 mg L-1  day-1 nitrogen, 0.2-1.1 mg L-1  day-1 P) compared with the leachate-chemical phosphate medium (1.2-4.7 mg L-1  day-1 nitrogen, 0.3-1.4 mg L-1  day-1 P). This study showed that WP is a suitable P source for microalgal cultivation over a range of salinities. To date, this is the first study demonstrating that raw WP can replace mineral P fertilizer for algal cultivation. PRACTITIONERS POINTS: Whey permeate is a comparable phosphorus source to standard fertilizers used in algal cultivation. Green algae removed phosphorus effectively from whey permeate. Microalgal cultivation is a good approach for treatment of whey permeate in combination with a nitrogen-rich wastewater.

Functional Diversity Facilitates Stability Under Environmental Changes in an Outdoor Microalgal Cultivation System.

Functionally uniform monocultures have remained the paradigm in microalgal cultivation despite the apparent challenges to avoid invasions by other microorganisms. A mixed microbial consortium approach has the potential to optimize and maintain biomass production despite of seasonal changes and to be more resilient toward contaminations. Here we present a 3-year outdoor production of mixed consortia of locally adapted microalgae and bacteria in cold temperate latitude. Microalgal consortia were cultivated in flat panel photobioreactors using brackish Baltic Sea water and CO2 from a cement factory (Degerhamn, Cementa AB, Heidelberg Cement Group) as a sustainable CO2 source. To evaluate the ability of the microbial consortia to maintain stable biomass production while exposed to seasonal changes in both light and temperature, we tracked changes in the microbial community using molecular methods (16S and 18S rDNA amplicon sequencing) and monitored the biomass production and quality (lipid, protein, and carbohydrate content) over 3 years. Despite changes in environmental conditions, the mixed consortia maintained stable biomass production by alternating between two different predominant green microalgae (Monoraphidium and Mychonastes) with complementary tolerance to temperature. The bacterial population was few taxa co-occured over time and the composition did not have any connection to the shifts in microalgal taxa. We propose that a locally adapted and mixed microalgal consortia, with complementary traits, can be useful for optimizing yield of commercial scale microalgal cultivation.