Open AccessOptimized culturing conditions for an algicidal bacterium Pseudoalteromonas sp. SP 48 on harmful algal blooms caused by Alexandrium tamarense
Author(s) -
Lyu YiHua,
Zhou YueXia,
Li Yi,
Zhou Jin,
Xu YiXiao
Publication year - 2019
Publication title -
microbiologyopen
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.881
H-Index - 36
ISSN - 2045-8827
DOI - 10.1002/mbo3.803
Subject(s) - alexandrium tamarense , pseudoalteromonas , fermentation , biology , food science , bacteria , microbiology and biotechnology , bioreactor , algal bloom , botany , phytoplankton , nutrient , 16s ribosomal rna , ecology , genetics
Bacteria play an important role in preventing algal blooms and reducing their harm to the environment. To improve the algicidal activity of Pseudoalteromonas SP 48 which had an inhibition effect on dinoflagellate Alexandrium tamarense , its growth medium and fermentation conditions were optimized for this bacterium. In this study, we used two steps to establish the optimum conditions. First, the proper proportion of medium was selected based on an orthogonal design. Then, the fermentation conditions were further optimized through uniform design in an enlarged 5L bioreactor. To test the algicidal ability of Pseudoalteromonas SP 48 under the optimum conditions, algal cell morphology was observed by transmission electron microscopy ( TEM ). After the orthogonal design, we found that the optimum medium was [0.7% (m/v) tryptone, 0.2% (m/v) soluble starch, 0.2% (m/v) sucrose, 0.1% (m/v) Fe SO 4 , and 1.2% (m/v) K 2 HPO 4 ] for Pseudoalteromonas SP 48 growth. Based on these results, optimum fermentation conditions were further explored in a 5L fermentation cylinder using a uniform design; the influence of variables such as incubation time, carbon type, and rotation speed were tested. The optimal fermentation conditions were fermentation time (42 hr), tryptone (1.1%), seeding volume (1.4 × 10 13 cells), and rotation speed (250 r/min). Under these established optimum conditions, the biomass of strain SP 48 increased by 79.2% and its lethal dose 50% ( LD 50 ) decreased by 54.0%, respectively. The TEM results showed that compared with the control group, the cell wall and cell membrane of A. tamarense were significantly damaged, and the structure and shape of the organelles were destroyed by algicidal bacteria of Pseudoalteromonas SP 48. Overall, our results demonstrate that the optimized culture conditions could significantly enhance the algicidal activity of Pseudoalteromonas SP 48 against a harmful dinoflagellate, such as A . tamarense . It will effectively provide a scientific foundation for both production of algicidal substances and HAB s control.