Rattiya Ongmali, Saranya Phunpruch and Usarat Thawornchaisit

pp. 359 - 365

Abstract

Cell growth and lipid production of a heterotrophic bacterium, R4.4 which accumulated the highest lipid content
among 12 bacterial colonies being isolated from wastewater of a poultry processing plant in Thailand, were evaluated in this
study. The culture was identified as Aeromonas sp. by 16S ribosomal DNA sequencing analysis.The highest lipid content was
obtained when the cells were in the early stationary growth phase compared to the cells in the exponential and the late
stationary phase. Over 50% of the fatty acid production by Aeromonas sp. KMITL-R4.4 were unsaturated fatty acids, including linoleic acid (C18:2, 43.2%), oleic acid (C18:1, 19.0%), and palmitoleic acid (C16:1, 8.2%). The culture had a preference for
glucose and fructose as seen from the maximum biomass and lipid contents that were obtained. Among volatile fatty acid
(VFA) species tested, acetic acid was the preferred substrate for lipid production but not favorable for cell growth.
In addition, ammonium sulfate was found to be the best among nitrogen sources tested. The C/N ratio exerts significant
impact on lipid production as seen from an increase of the lipid content from 10.8% to 18.2% by exposing the bacterial cells
to a medium with lower nitrogen concentration (0.1g/l) and higher level of glucose (28 g/l).

Keywords

• heterotrophic bacterium
• lipid accumulation
• medium components
• microbial lipid