Algal–bacterial synergy in treatment of winery wastewater

Abstract There is significant potential for employing algae in tertiary wastewater treatment, however, little is known about the contribution of algae-bacteria synergy toward treatment performance. This study demonstrates potential synergy in the treatment of three winery wastewater samples. Two strains of green algae, Auxenochlorella protothecoides and Chlorella sorokiniana were tested and each removed > 90% of nitrogen, > 50% of phosphate, and 100% of acetic acid in the wastewater. Both algae strains grew significantly faster on wastewaters compared to growth on minimal media. Organic carbon in the wastewater apparently played a limited role in algal growth enhancement. When cultured on sterile-filtered wastewater, A. protothecoides increased soluble COD loadings in two of the three wastewaters and C. sorokiniana secreted an insoluble film. Culturing algae with the native wastewater microbial community negated the secretion of algal photosynthate, allowing for simultaneous reductions in COD and nutrient concentrations. Both algae species stimulated bacterial growth in a strain-specific way, suggesting unique responses to algal photosynthate. Cofactor auxotrophy for thiamine, cobalamin, and biotin is widespread among algae and these cofactors are typically obtained from bacteria. Sequencing the wastewater microbial community revealed bacteria capable of synthesizing all three cofactors while liquid chromatography with mass spectrometry (LCMS) and bio-assays revealed the presence of thiamine metabolites in the wastewaters. These cofactors likely increased algal growth rates, particularly for A. protothecoides , which cannot synthesize thiamine de-novo but can salvage it from degradation products. Collectively, these results demonstrate that bacteria and algae provided synergistic growth benefits, potentially contributing to higher levels of wastewater treatment than either organism type alone.