EFFECT OF MICROALGAE-ASSOCIATED BACTERIA ON THE GROWTH OF Botryococcus braunii Kϋtzing 1849

Muhamad A.R. Ridzuan1, *, Fatimah Md. Yusoff1, 2, Yam Sim Khaw1, and Fatin M.I. Natrah1, 2
1Laboratory of Marine Biotechnology
Institute of Bioscience
Universiti Putra Malaysia
43400 UPM Serdang
Selangor, Malaysia
 
2Department of Aquaculture
Faculty of Agriculture
Universiti Putra Malaysia
43400 UPM Serdang
Selangor, Malaysia
mdridzuan.rahim@gmail.com

Microalgae have high commercial value in addition to their crucial role in providing energy in the aquatic food chain. They are valuable sources of various compounds such as antioxidants, fatty acids and amino acids that can be utilized in food, nutraceutical, pharmaceutical, and aquaculture industries. Among many microalgae species, Botryococcus braunii is well known for its high lipid content and its potential application in renewable energy industry. However, its slow growth rate is a major hindrance to be utilized commercially. This study aimed to examine the bacterial community and its interaction with Botryococcus braunii in influencing the growth of latter. The Botryococcus braunii (UPMC-A0021) was isolated and purified from Putrajaya Lake, Malaysia, and its identity was confirmed based on its morphology (light and scanning electron microscope) and DNA sequences (PCR method). Symbiotic bacteria were isolated and identified from the microalga-growing culture. Each isolated bacteria was added into an axenic microalgae culture respectively to examine the effect of bacteria on the microalga growth. Nine different heterotrophic bacteria were living symbiotically with B. braunii. These bacteria were classified into four distinct phyla, Actinobacteria, α-proteobacteria, β-proteobacteria and γ-proteobacteria. Five isolated bacteria particularly Rhizobium sp. demonstrated synergistic relationship with B. braunii. The growth pattern of B. braunii with or without bacteria was not significantly different for 25 days. However, B. braunii culture with the inoculation of Rhizobium sp. showed significantly higher (p <0.05) biomass compared to the other bacterial inoculation. This study illustrated that the symbiotic bacteria could be utilized as inoculants for microalga culture to optimize the growth and biomass production of B. braunii.  

Keywords: Microalgae, Botryococcus braunii, bacteria, growth rate, microalgae-bacterial interaction.