Mixotrophic culture of bait microalgae for biomass and nutrients accumulation and their synergistic carbon metabolism.

Microalgae cannot meet the bait demand for aquaculture due to light intensity limitation and other disadvantageous conditions. This research selected 6 mixotrophic microalgae, and the optimal strains and organic carbon were screened. The results showed that Thalassiosira pseudonana and Chlorella sp. are suitable for mixotrophic culture. The maximum cell density of Thalassiosira pseudonana was found to be 1.67 times than that of the photoautotrophic group when glycerol was added. The maximum cell density of Chlorella sp. with acetic acid was 1.69 times than that of the photoautotrophic group. When the concentration of acetic acid was 5.0 g·L-1 and the concentration of KNO3 was 0.2 g·L-1, the maximum biomass of Chlorella sp. could reach 3.54 × 107 cells·mL-1; the maximum biomass of Thalassiosira pseudonana was 5.53 × 106 cells·mL-1 with 10.0 g·L-1 glycerol and 0.2 g·L-1 KNO3. Metabolomic analysis further revealed that mixotrophic bait microalgae could promote the accumulation of lipids and amino acids.

Improved growth of bait microalgae Isochrysis and aquacultural wastewater treatment with mixotrophic culture.

This research of mixotrophic microalgae Isochrysis 3011 with glycerol was combined with the treatment of aqua-cultural wastewater, different initial concentrations, and optimized light intensities. The algae growth rate, removal efficiencies of total nitrogen (TN) and total phosphorus (TP) were determined. Results showed that the suitable initial concentration was 0.4 g L-1, and the optimum light intensity was 60 µmol m-2 s-1. The growth of the mixotrophic group was better than that of the autotrophic culture. The biomass yield of the mixotrophic group with glycerol was 0.17 g L-1 d-1, and the removal rates of TN and TP were 73.39% and 95.61%, respectively. The content of total lipid and total protein in mixotrophic group were higher than the values of the autotrophic group. This indicates that aquaculture wastewater treatment with mixotrophic bait microalgae can obtain superior micro-algal biomass, which is also a potential technology for wastewater utilization and ecological protection.

Modeling and improving arrayed microalgal biofilm attached culture system.

A microalgal biofilm-attached-system is an alternative cultivation method, that offers potential advantages of improved biomass productivity, efficient harvesting, and water saving. These biofilm systems have been widely tested and utilized for microalgal biomass production and wastewater treatment. This research a microalgal growth model for the biofilm attached culture system has been developed and experimentally validated, both, in single and arrayed biofilm systems. It has been shown that the model has the capability to accurately describe microalgae growth. Moreover, via the model simulation, it was observed that system structural parameters, light dilution rate, and light intensity significantly affected the culture performance. The limitations, and improvement aspects of the model, are also discussed in this study. To our knowledge, this is the first time that a mathematical model for an arrayed-biofilm-attached-system has been developed and validated. This model will certainly be helpful in the design, improvement, optimization, and evaluation of the biofilm-attached-systems.

Screening of the dominant Chlorella pyrenoidosa for biofilm attached culture and feed production while treating swine wastewater.

This research 12 microalgal species were screened for biofilm attached culture in the treatment of anaerobically digested swine wastewater (ADSW). The influence of ADSW on biomass productivity and removal efficiencies were evaluated using biofilm attached culture with the selected Chlorella pyrenoidosa. The variation of nutritional components from algal cells were further analysed to evaluate the potential applications of C. pyrenoidosa. The results showed that C. pyrenoidosa had the highest tolerance to ADSW, and the highest removal efficiencies for wastewater pollutants were reached when cultured in 5 times diluted ADSW. These test conditions resulted in an algal cell biomass composed of 57.30% proteins, 14.87% extracellular polysaccharide, 3.08% crude fibre, 5.57% crude ash, 2.85% moisture. Amino acids in proteins contained 21.73% essential amino acids and the EAA/NEAA value was 0.64. The essential amino acid score indicates that the selected C. pyrenoidosa could be a good protein source for feed addition.