title: Optimization of Chlorella vulgaris and bioflocculant-producing bacteria co-culture: enhancing microalgae harvesting and lipid content.
abstract: Microalgae are a sustainable bioresource, and the biofuel they produce is widely considered to be an alternative to limited natural fuel resources. However, microalgae harvesting is a bottleneck in the development of technology. Axenic Chlorella vulgaris microalgae exhibit poor harvesting, as expressed by a flocculation efficiency of 0·2%. This work optimized the co-culture conditions of C. vulgaris and bioflocculant-producing bacteria in synthetic wastewater using response surface methodology (RSM), thus aiming to enhance C. vulgaris harvesting and lipid content. Three significant process variables- inoculation ratio of bacteria and microalgae, initial glucose concentration, and co-culture time- were proposed in the RSM model. F-values (3·98/8·46) and R(2) values (0·7817/0·8711) both indicated a reasonable prediction by the RSM model. The results showed that C. vulgaris harvesting efficiency reached 45·0-50·0%, and the lipid content was over 21·0% when co-cultured with bioflocculant-producing bacteria under the optimized culture conditions of inoculation ratio of bacteria and microalgae of 0·20-0·25, initial glucose concentration of <1·5 kg m(-3) and co-culture time of 9-14 days. This work provided new insights into microalgae harvesting and cost-effective microalgal bioproducts, and confirmed the promising prospect of introducing bioflocculant-producing bacteria into microalgae bioenergy production.
  
  
  CONCLUSIONS
  This work optimized the co-culture conditions of microalgae (C. vulgaris) and bioflocculant-producing bacteria (F2, Rhizobium radiobacter) in synthetic wastewater using response surface methodology, aiming to enhance C. vulgaris harvesting and lipid produced content. Bioflocculant-producing microbes are environmentally friendly functional materials. They avoid the negative effects of traditional chemical flocculants. This work provided new insights into microalgae harvesting and cost-effective production of microalgal bioproducts, and confirmed the promising prospect of introducing bioflocculant-producing bacteria into microalgae bioenergy production.
authors.affiliation: Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun, China.
authors.forename: Y
authors.initials: Y
authors.lastname: Wang
authors.forename: Y
authors.initials: Y
authors.lastname: Yang
authors.forename: F
authors.initials: F
authors.lastname: Ma
authors.forename: L
authors.initials: L
authors.lastname: Xuan
authors.forename: Y
authors.initials: Y
authors.lastname: Xu
authors.forename: H
authors.initials: H
authors.lastname: Huo
authors.forename: D
authors.initials: D
authors.lastname: Zhou
authors.forename: S
authors.initials: S
authors.lastname: Dong
mesh_terms: D016960:Agrobacterium tumefaciens / Q000254:growth & development / Q000378:metabolism*; D056804:Biofuels; D048408:Chlorella vulgaris / Q000254:growth & development / Q000378:metabolism*; D018920:Coculture Techniques; D004734:Energy Metabolism / Q000502:physiology; D005427:Flocculation; D008055:Lipids / Q000096:biosynthesis; D058086:Microalgae / Q000254:growth & development* / Q000378:metabolism*; D062065:Wastewater / Q000382:microbiology*
chemical_list: D056804:Biofuels; D008055:Lipids; D062065:Wastewater
keywords: bioflocculant-producing bacteria; co-culture; harvesting; lipid content; microalgae; optimization; response surface methodology