Lipid-extraction of Tribonema minus avoids foaming facilitating anaerobic co-digestion with molasses vinasse

Abstract

Tribonema minus, a filamentous microalgae, has great potential as an anaerobic digestion (AD) substrate, owing to its relatively low cultivation and harvesting costs. This is the first study to explore the effect of T. minus as an anaerobic co-digestion (AcoD) substrate with molasses vinasse (MV). To analyze the potential effects of the structure and composition of T. minus on the AD process, we conducted batch and semi-continuous AD using simple dehydrated T. minus (Fresh T. minus, FTR) and lipid-extracted and pulverized T. minus (Pretreated-T. minus, PTR). The results showed that the maximum methane production potential of FTR was 158.9 ± 2.9 mL CH4 g−1 VS, which was reduced by 25% after pretreatment. However, the methane production potential increased by 18% in the batch AcoD with MV. Meanwhile, FTR led to the accumulation of fatty acids and lipids, including palmitic acid, in semi-continuous AcoD with MV. Lipid accumulation further increased the polysaccharide and protein content in the extracellular polymeric substances, resulting in a decrease in liquid surface tension and an increase in foam formation, which ultimately led to a decrease in methane production potential and soluble chemical oxygen demand removal rate. Microbial community analysis demonstrated that PTR effectively mitigated the inhibitory effects caused by filamentous microalga (FM). Our results further elucidated the potential mechanism of foam formation during the AD of FTR and revealed that pretreatment can lead to effective recovery of products from T. minus while promoting methane production potential and optimizing the microbial community composition during AcoD. Therefore, our study provides novel insights into the utilization of FM.