title: Toward facilitating microalgae cope with effluent from anaerobic digestion of kitchen waste: the art of agricultural phytohormones.
abstract: BACKGROUND
  Although numerous studies have used wastewater as substitutes to cultivate microalgae, most of them obtained weaker algal viability than standard media. Some studies demonstrated a promotion of phytohormones on algal growth in standard media. For exploiting a strategy to improve algal biomass accumulation in effluent from anaerobic digestion of kitchen waste (ADE-KW), the agricultural phytohormones gibberellin, indole-3-acetic acid, and brassinolide (GIB) were applied toChlorellaSDEC-11 andScenedesmusSDEC-13 at different stages of algal growth. Previous studies have demonstrated a promotion of phytohormones on algal growth in standard media, but attempts have been scarce, focusing on wastewater cultivation system. In addition, the effects of wastewater on algal morphology and ultrastructure have not been revealed so far, much less on the mechanism of the role of phytohormones on algae.
  
  
  RESULTS
  ADE-KW disrupted the membranes of nuclear and chloroplast in ultrastructural cell of SDEC-11, and reduced the room between chloroplast and cell membrane and increased the starch size of SDEC-13. This reduced algal growth and biocompound accumulation, but SDEC-13 had greater adaptation to ADE-KW than SDEC-11. Moreover, inoculation with an algal seed pretreated with GIB aided the adaptability and viability of algae in ADE-KW, which for SDEC-13 was even promoted to the level in BG11. GIB mitigated the inhibition of ADE-KW on algal cell division and photosynthetic pigments and apparatus, and increased lipid droplets, which might result from the change in the synthesis and the fate of nicotinamide adenine dinucleotide phosphate. GIB addition significantly promoted lipid productivity of the two algal species, following 13 mg L-1d-1of SDEC-11 in B+ADE-KW and especially 13 mg L-1d-1of SDEC-13 achieved during the priming of algal seed with the hormones, which is 139% higher than 5 mg L-1d-1achieved in ADE-KW control.
  
  
  CONCLUSIONS
  Agricultural phytohormones could be applied as a strategy for promoting biomass and biocompound accumulation of algae in ADE-KW, in which pretreatment of the algal inoculum with hormones is a unique way to help algae survive under stress. Considering our results and treatment technology for kitchen waste, a more feasible and economic plant can be built incorporating anaerobic digestion, algae cultivation with ADE-KW assisted with phytohormones, and biodiesel production.
authors.affiliation: School of Environmental Science and Engineering, Shandong University, No. 27 Shanda Nan Road, Jinan, 250100 China.|Shandong Provincial Engineering Centre on Environmental Science and Technology, No. 17923 Jingshi Road, Jinan, 250061 China.
authors.forename: Haiyan
authors.initials: H
authors.lastname: Pei
authors.affiliation: School of Environmental Science and Engineering, Shandong University, No. 27 Shanda Nan Road, Jinan, 250100 China.
authors.forename: Liqun
authors.initials: L
authors.lastname: Jiang
authors.affiliation: School of Environmental Science and Engineering, Shandong University, No. 27 Shanda Nan Road, Jinan, 250100 China.
authors.forename: Qingjie
authors.initials: Q
authors.lastname: Hou
authors.affiliation: School of Environmental Science and Engineering, Shandong University, No. 27 Shanda Nan Road, Jinan, 250100 China.
authors.forename: Ze
authors.initials: Z
authors.lastname: Yu
keywords: Agricultural phytohormones; Algae biomass; Anaerobic digestion; Kitchen waste