Kamarudin, Mohd Salleh

Mat Jais, Abdul Manan

Muhamad Shaleh, Sitti Raehanah

Omar, Hishamuddin

Syed, Mohd Arif

Universiti Putra Malaysia Institutional Repository

FOR Category F10900: Agricultural SciencesA PRELIMINARY STUDY ON THE EFFECT OFMEDIA CONCENTRATION ON THE GROWTHEFFICIENCY AND THE BIOCHEMICALCOMPOSITION OF FRESHWATER MICROALG'ASCENEDESMUS SP.Hishamuddin Bin Omar, M.S.R. Shaleh, M.A. Syed,M.S. Kamarudin and A.M ..M. JaisFaculty of Science ana Environmental StudiesUniversiti Putra Malaysia, 43400 UPM, Serdang, Selangor,MalaysiaKeywords: phytoplankton, laboratory culture, mediaconcentration, growth and biochemical profile.IntroductionLike many other organisms, the availability of nutrients isone of the primary factors regulating the growth, reproduc-tion and biochemistry of phytoplankton. Nitrogen has oftenbeen cited to be the primary nutrient limiting phytoplanktonproduction in the world's oceans. It has been reported thatcells can live in high nitrate concentrations with no lethal ef-fect but showed a decrease in biomass and growth Isochrysisgalbana, for example, can double the fatty acid content innitrate-grown cells but contains lower concentration and onlyfew amino acids (Flynn et al. 1992). Many researchers havestudied the effect of limiting nitrate concentration on algalgrowth by altering the molarity of certain nitrate sources inthe growth media. In this paper we examine the effect of me-dia concentration on the growth and the biochemical contentsin Scenedesmus sp.Materials and MethodsAlgal culture Scenedesmus sp. used in this study was ob-tained from the COMAS Culture Collection of microalgae.Axenic batch cultures were grown in 5 liters flasks at 22 ±2°C on 24:0 (light: dark) cycle with Triton™ coolwhite fluo-rescent light which delivered 90~molm2s1 irradiance. Cul-tures were maintained in distilled water enriched with BBMgrowth media (Nichols, 1973). The growth media were pre-pared in two different concentrations; one at full concentra-tion and the other at half concentration. After 10 days, thecells were harvested by centrifugation at 5000 rpm for 3 min.The pellets of the cells obtained were combined and trans-ferred into cryovials and frozen at -80°C prior to freeze-drying. For chlorophyll. determination, 10 ml cell suspen-sions were harvested daily and filtered onto cellulose mem-brane filter. The filter paper containing cells was homoge-nized and extracted with acetone: DMSO (5:1) mixture (v/v)and stored for 24 h in dark refrigerator for pigment extrac-tion. The extracts were centrifuged at 3000 rpm for 3 minand Chlorophyll. was determined spectrophotometrically.Total protein was determined using the dye binding methodsAbout 3-5 mg freeze dried samples were homogenized in0.5N NaOH after 5 min sonication in DMSO. The homogen-ates were kept for 24 h at room temperature for complete ex-traction. The extracts were finally assayed with alkaline cop-per reagent to get the colour reaction. The carbohydrateswere analysed by the colorimetric phenol-sulphuric acidmethod after hydrolysis in 2N HCI for 1 h at 80°C. For lipidextraction, a 30-40 mg sample was extracted using CHCI3:MeOH:H20 (1:1:0.9 v/v/v) and determined gravimetrically.Results and DiscussionThe chlorophyll. contents were measured daily for 10 days toobserve cell growth. The results obtained indicated that therewas no lag phase observed because of the high inoculationrate (20%). Cells grown at full concentration yielded thehighest chlorophyll. on the 9th day and started to decrease onthe 10th day. However, the cells grown in low media con-centration exhibited a faster growth but the growth lastedonly for 5 days. The biochemical contents also changed withchanges in the media concentration. The reduction in cell ni-trogen at low media concentration led to a decrease in chlo-rophyll. content which indicated a reduction in the protein-rich chloroplast apparatus as well as the lipids in the chloro-plast membranes. The total proteins and lipids diminished asthe media concentration decreased (from 29.40 ± 0.69% to19.91 ± 0.06% and from 33.02 ± 0.51 to 22.03 ± 0.54% re-spectively). However, total carbohydrate production washigher in low media concentration (34.80 ± 0.37%) com-pared to full concentration (28.77 ± 1.07%).The media concentration can be manipulated to affect thegrowth rate and formation of major biochemical constituents.As reported previously, high nitrate concentration in the cellsleads to a decrease in the cell density and photosyntheticpigment content (Jimenez and Niell, 1991). From the resultswe observed that at low nitrate concentrations cells grewfaster but lasted only for 5 days after which the growth rateslowed down approaching stationary phase. Under halfstrength media, we also observed a high percentage of carbo-hydrate. Probably in the late stationary stage mature cellscontain more carbohydrate. It has been reported that in abatch mode, microalga can produce high levels of proteinand low carbohydrate and lipid during the logarithmic phase,but contains more carbohydrate at the stationary stage(Brown et al. 1993).ConclusionsOur study indicated that the biochemical compositions canvary if the cells are harvested at different growth phases.Further studies to harvest the cells at the 5th day and 9th dayof cultivation of cultures under half strength and full strengthmedia, respectively are being planned.ReferencesBrown, M.R., Garland, C.D., Jeffrey, S.W., Jameson, 1.0. and Leroi,J.M. 1993. The gross and amino acid compositions of batch andsemi-continuous cultures of Isochrysis sp. (clone T.lSO), Pavlovalutheri and Nannochloropsis oculata. 1. Appl. Phycol. 5: 285-296.Flynn, K.J., Garrido, J.L., Zapata, M., Opik, H. and Hipkin, C.R.1992. Changes in fatty acids, amino acids and carbon/nitrogenbiomass during nitrogen starvation of ammonium- and nitrate-grown Isochrysis galbana. 1. Appl. Phycol. 4: 95-104.Jimenez, C. and Niell, F.X. 1991. Growth of Dunaliella viridis Teo-doresco. Effect of salinity, temperature and nitrogen concentra-tion.l. Apply. Phycol. 3: 319-327.Nichols, H.W. 1973. Growth Media-Freshwater. In: Handbook ofPhycological Methods Culture Methods and Growth Measure-ments. Stein, J.R. (Ed.). Cambridge University Press, USA. p. 7-24.Supponed by IRPA Grant 01-02-04-0162141

A preliminary study on the effect of media concentration on the growth efficiency and the biochemical composition of freshwater microalga Scenedesmus sp.

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A preliminary study on the effect of media concentration on the growth efficiency and the biochemical composition of freshwater microalga Scenedesmus sp.

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