Design and characterization of bioreactor based on oxygen mass transfer coefficient for biomass and fatty acid production of aurantiochytrium limacinum buchaxm 122
Abstract:
Aurantiochytrium limacinum BUCHAXM 122is a marine microorganism from a group of thraustochytrids. It was capable of producing extracellular enzyme proteases, lipase, urease, α-Glucosidase and phosphatases. From the study of the growth of GYP broth incubator shaker at 200 rpm at 25°C for 168 hours a highest biomass was recorded at 26.17±0.23 g/L at 108 hours and found various kinds of fatty acids. Among the fatty acids that can be converted to a renewable energy source (Biodiesel) is PA (Palmitic acid, PA) with highest value at 211.62±24.56 mg/g DW (42.87±1.06% of total fatty acids) and DHA (Docosahexaenoic acid, DHA) Omega-3 measured highest value at 156.91±8.69 mg/g DW (30.31±5.88% of total fatty acids) with cell elements composed of Carbon (C)57%, Hydrogen (H) 9%, Nitrogen (N)4.45%, Sulfur (S)1% and Oxygen (O)29%. The increase in the efficiency of production towards desiging the three bioreactors: stirred type bioreactor, bubble column bioreactor and internal air lift type bioreactor is based on oxygen mass transfer coefficient by sulfite method in distilled water comparing with incubator shaker. It was found that the appropriate oxygen mass transfer coefficient within each bioreactor were by using 8 super fine bubble air stones therein. Stirred type bioreactor at 600 rpm, bubble column bioreactor with aeration rate at 3 vvm and in an internal loop airlift type bioreactor with aeration rate at 3 vvm. The results showed that only values from the stirred type bioreactor were higher than those of the shaker (p< 0.05).
When culturing A. limacinum BUCHAXM 122, the appropriate state as mentioned in each bioreactor where air was introduced at 3 vvm leading to an overflow of air bubbles bubbling out of the bioreactor, consequently, air was later introduced at 2 vvm in the stirred type bioreactor and bubble column bioreactor and 1.5 vvm in the internal loop airlift type bioreactor it was found a highest biomassat 43.05±0.35 g/L in stirred type bioreactor at 48 hours, which was the highest cultured time in other bioreactors (p< 0.05). Whereas, in an air lift type bioreactor and bubble column bioreactor, the highest values were around the same at 37.60±4.60 g/L and 38.55±3.82 g/L 120 hours into the cultured time respectively and those in an incubator shaker with the lowest biomass measuring out at 32.90±0.28 g/L 120 hours into the cultured time. The dissolved oxygen level during culturing affects the growth and production of fatty acids. Consequently, adjustment was made to air levels during culture A. limacinum BUCHAXM 122 in stirrer bioreactor for 120 hours under the following 3 conditions: 1) Adding only air 2) Adding both air and pure oxygen at a ratio of 1:1; and 3) Adding air and pure oxygen at a ratio of 1:1 and reducing both air and pure oxygen at 48-120 hours into the experiment. The results of the 1st and 3 rd conditions, at the 48th hour into the experiment, had no significant differences on biomass (p> 0.05) where biomass values are 29.95±0.07 and 29.25±2.90 g/L respectively. However, the biomass in the 3rd condition at 48 hours and 72 hours into the experiment had no significantdifferences (p> 0.05). Large amounts of PA and DHA were found in the 1st condition, at 48 hours into the experiment, they have values 403.20±20.83 mg/g DW (59.87±4.98% of total fatty acids) and 129.72±6.42 mg/g DW (19.26±1.56% of total fatty acids) respectively