Tgp chi Khoa hgc Tnr&ng £>gi hgc Cdn Tha Phdn B: Ndng nghiep. Thuy san va Cdng nghi Sinh hgc: 26i2(i!3i. 180-1S
Tap chf Khoa hpc Tri/cJng Oai hoc Can Thd website: sj. ctu. edu. vn
ANH HirOfNG CUA CAC MlTC NITO KHAC NHAU LEN SINH TRU^^NG, HAM LU'gfNG PROTEIN VA LIPID CUA TAD Spirulina platensis (Geitler, 1925) NU6l TRONG N u ' d c MAN
Trdn Thi Le Trang'
' Khoa Nudi trdng Thdy sdn. Trudng Bgi hgc Nha Trang Thdng tin chung:
Ngaynhdn: 22/01/2013 Ngdy chdp nhdn: 20/06/2013 Title:
Effect of nitrogen levels on gro\i'th. protein and lipid content of Spirulina platensis (Geitler, 1925) cultured in seawater
Tir khoa:
Hdm lugng protein vd lipid, nita, sinh trudng. Spirulina platensis
Keywords:
Growth, nitrogen, protein and lipid content. Spirulina platensis
ABSTRACT
In this study. 5 levels of nitrogen (618: 12.35; 18.53: 24.7 and 30 88 mg/l) were tested in order to evaluate the effect of this nutrient on growth, protein and lipid content of S. platensis cultured in sea»-ater under laboratory conditions The results showed that, the alga cultured at higher nitrogen levels (18.53; 24.7 and 30.88 mgd) gave higher maximum biomass (4.90; 4. and 4 35 gl) compared to the lawer levels (6.18 and 12.35 mg,1) (3.06 and 3.46 g/l) (p < 0.05) which aehie\'ed on day 8. However, there were no significant differences about maximum biomass gained among nitrogen levels of 18 53; 24.7 and 30.88 mg/l or 6.18 and 12.35 mg/l (p > 0.05). Similarily, the highest nitrogen levels gave the highest content of protein but lowest content of lipid and vice versa. Specifically, the highest nitrogen levels (30,88 mg/l), the protein and lipid contents obtained 69.64 and 10.12% of the total dry weight, respectively while this figures at the lowest nitrogen level (6.18 mg/l) were 52.29 and 13.48% ofthe total dry weight, respectively (p < 0.05).
Summary, the most suitable nitrogen level for culturing S. platensis was 18-53 mg/l in order to obtain the optimal values of growth, protein as well as lipid content and economic efficiency.
T O M TAT
Trong nghien ctru ndy. 5 mirc nito (6.18; 12,35; 18,53: 24.7 vd 30,88 mg/l) dugc thir nghiem nhdm ddnh gid dnh hirdng cua yeu td nd\- len sinh trudng, hdm lurmg protein vd lipid cua tdo S. platensis nudc man trong diiu kien thi nghiem. Ket qua cho thdy. tdo dirge nudi d cdc miic nita cao hon (18.53: 24.7 \d 30,88 mg/l) cho sinh khdi cue dgi ldn han (4.90;
4.79 vd 4,35 g/L) so vdi cdc muc nifa thdp han (6,18 vd 12,35 mg/l) (3.06 vd 3.46 g/L) (p < 0.05) a ngdy nudi thd S. Khdng cd su klidc biet thdng ke vi sinli khdi cue dgi dgt dugc giOa cdc mdc nito 18,53; 24.7 vd 30,88 mg/I hay 6,18 vd 12.35 mg/l (p> 0.05). Tuang tu, cdc miic nita cdng cao hdm lugng protein dgt dirge cdng cao nhung hdm luang lipid dgt dugc lgi cdng thdp vd nguac lgi. Cuthe, a muc nita cao nhdt (30.88 mg/li hdm luang protein vd lipd dat dugc ldn luat Id 69,64 vd 10,12% khdi lugng kho. trong khi do. con sd nd\- d muc nita thdp nhdt (6.18 mg/l) ldn lugt la 52.29 vd 13,48% khdi lugng kho (p < 0.051 Cd the thdy rdng. muc nita tdt nhdt cho tdo S. platensis Id 18,53 mg/l nhdm d0 dugc cdc gid tri tdi uu vi sinh trudng, hdm luang protein, lipid vd hieu qud kmh ti.
180
Tap chi Khoa hoc Tni&ng Dai hgc Cdn Tha Phdn B: Nong nghiip Thuy san va Cong ngM Sinh bgc: 26 <2013): 180-18?
1 DAT VAN DE
Tao Spirulina platensis la mfit loai ldo lam cd gia tti dinh dudng rdt cao, ddc biel la ham lugng protein chilm ldi 56 - 77% khdi lugng khfi, gidu vitamin, chat khoang, axit amin va cac axit beo thilt ylu (Belay, 2002; Gershwin, 2007; Falquet, 1997; Tang & Suter, 2011).
Ngoai ra, khd nang thich ung tdt vdi cdc yeu Ifi mfii trudng, dieu kien va ky thudt nudi kha don gian cung la mdt trong nhung Igi the khi nudi sinh khdi lodi ldo nay (Ahsan vd ctv., 2008).
Chinh vi vay, tao Spirulina da dugc nghien cuu, san xuat vd ung dung uong nhieu lmh vuc cua ddi sdng. Tdo Spirulina cung vdi cac san pham cua chiing dugc su dung rdng rai lam thuc phdm chuc ndng, ngudn dinh dudng bfi sung thiet yeu, thudc chua benh (ung thu, HIV/AIDS, viem gan, tieu dudng,...), my phdm (chdm soc da va tdc), thuc an chan nudi vd xu ly nudc thdi (Belay, 2002; Ahsan vd ctv., 2008; Duong Thi Hodng Oanh vd ctv., 2002; Falquet. 1997; Cifferi va Tiboni, 1985;
Richmond, 1986).
Trong nudi tao ndi chung, ngudn tao gifing, chdt dinh dudng va dieu kien mfii trudng nufii la nhiing yeu tfi dnh hudng rdt Idn den sinh trudng va thanh phan sinh hda cua tao. Cdc thanh phdn dinh dudng da lucmg (carbon, nito, phdt pho) va vi lugng anh hudng rat Idn den sinh trudng cua tao, ddc biel trong dieu kien nudi vdi mat do cao (Costa vd ctv., 2003;
Lavens va Sorgeloos, 1996: Vonshak vd en-..
1996; Richmond vd ctv., 1986; Tran Thi Le Trang va crt'., 2012). Cdc muc nita khdc nhau trong mfii trudng nudi cd dnh hudng Idn den sinh trudng, ham lugng protein va lipid cua tao da dugc de cap trong nhieu nghien cuu. Thilu hut nito la ngujjen nhan lam giam tdc do sinh trudng, sinh khdi, thdi gian duy tri mat do cue dai. hdm lugng sSc tfi, protein, lipid, axil beo khong no, vitamin, carotenoids, phycocianin, enzyme,... d nhieu lodi ldo trong dd cd tao S.
platensis (Cohen. 1999: Piorreck vd ctv., 1984;
Tedesco va Duerr. 1989: De Loura va ctv., 1987; Olguin vd en-., 2001; Uslu vd cU:, 2011). Ngoai ra, mdi trudng nudi (nudc nggt hay nudc man) va ngufin nita khdc nhau (NO3', NO:'. NH4"....) cung anh hudng din nhu cau
nita cua tao (Prabakaran va Ravindran, 2012;
Li vd ctv., 2008).
Nhilu nghien cuu da chi ra rang, tao Spirulina nudi trong mdi trudng nudc man cd gia tri dinh dudng vugt trgi ban so vdi nudi trong nudc nggt the hien d so lugng chat co hoat tinh sinh hgc cao (polysaccharides, inositol va phycocyanin). cac nguyen td vi luang, ham lugng protein, lipid, cac axil beo thiet ylu (DHA, EPA, ARA, LA, LOA,...) (Falquet, 1997; Cifferi va Tiboni, 1985). Tdo Spirulina nudi trong mdi trudng nudc man con de tieu hda va hap thu han so vdi nufii ttong nudc nggt (Ahsan vd ctv., 2008). Ngoai gia tri dinh dudng cao. nudi tdo Spirulina trong nudc man cdn gdp phan tiet kiem mgt lugng ldn cac chat khoang da lugng, vi lugng bd sung va tan dung tdt tiem nang dien tich nudc man sdn c6 d nudc ta. Tuy nhien, cac nghien cuu ve nufii tdo Spirulina Irong nudc man hau nhu chua dugc de cap. Chinh vi vay, nghien cuu dugc thuc hien nham xdc dinh mdc nita tfii tm cho nudi tao Spirulina nudc man trong dieu kien thi nghiem. Day Id mdt trong nhung tien de de thiet lap quy trinh cfing nghe nudi sinh khoi loai tdo nay d quy md cdng nghiep phuc vu nhu cdu cho con ngudi.
2 PHlTONG PHAP NGHIEN C i r u 2.1 Vat li^u nghien ciru
Ddi tugng nghien cuu la tao Spirulina platensis. Day la lodi tao cd ngudn gdc nudc nggt nhtmg da dugc thudn hda trong moi trudng nudc man (30%o). Nghien cuu dugc thuc hien tai Phdng Thuc tap Sinh ly - Sinh thai, Trudng Dai hgc Nha Trang.
Ngudn nudc bien dugc xu ly bdng Chlorine 25 ppm ttong 2 ngay, sau dd phai ndng va trung hda bang Natrithiosulfale vdi ty le 1:1.
Trudc khi thi nghiem, nudc bien dugc tiet triing bdng each hap d ni'^C, 25 aim Uong 15 phut. Tao dugc thi nghiem trong cdc Ig thiiy tinh cd thi tich la 500 mi. Mdi trudng dinh dudng dugc su dung ttong nghien cuu nay la f 2 Guillard (Lavens va Sorgeloos, 1996).
2.2 Bo tri thi nghiem
Nghien cuu anh huofng cua cdc muc nito khac nhau len sinh trudng ham lugng protein
T^ chi Khoa hgc Tru&ng Dgi hgc CAt Tha Phdn B: Nong nghiip. Thuy- san va Cdng nghi Sinh l^c: 26 '2(113,. isru/i- va lipid cua tao S. platensis dugc thuc hien
tren c a sd ham lugng nita cd trong mdi trudng nudi f/2 (12.35 mg N/l) theo cac ti Ie 0,5: 1.0:
1.5; 2,0 va 2.5 lan. Ndi each khac. thi nghiem dugc bd tri tuang ung vdi 5 nghiem thuc lan lugt la: 6,18; 12.35; 18.53: 2 4 . 7 ^ 3 0 . 8 8 m g X l . Ngudn nito dtrgc sir dung cho nghien cuu nay d dang NaNOj. Mdi nghiem thuc dugc thuc hien vdi 3 lan lap. Sinh khfii tao ban ddu la
\A6e/\.
Cac yeu td mdi trudng, ngoai nita, dugc du)- tri ttong pham \ i thich hgp vdi sinh trudng cua tao S. platensis: nhiet do phdng 25^C. pH 8, che dg chieu sang 16 gid sdng: 8 gid toi. sue khi lien tuc 24/24, cudng do anh sang 3.000 lux. do man 30%o.
23 Phirong phap thu thap va xir ly so lieu Phuang phdp thiet lap ducmg chudn moi
quan he gjira OD vd khoi loang kho cua Ido:
Mat dp quang (Optical Density: OD) cua tao dugc xac dinh bang each lay 5 ml dung dich tao dtra vao may do quang phd (Specuophotometer CECIL CE 1011, lOlS, 120554) d budc sdng 560 nm. Ddng thdi, tien hanh xac dinh khdi lirgng khd ciia tao. De .xac dinh khdi lugng khfi ciia lao, tien hanh Igc mau dich ldo b ^ g gidy lgc cd kich c6 mat ludi 5 jun. Sau khi Igc. tiln hanh sd> khd tao d nhiet do 80°C trong 4 gid (Richmond va ctv., 1986).
Khdi lugng khd cua tao dugc can bang can dien tu Precisa XT 220A vdi do chinh xac 0.001 g. Mdi quan he hdi quy tuyen tinh giua OD va khdi lugng khd cua tao dugc xac djnh theo phuang phap cua Lavens \ a Soi^eloos (1996) vdi phuong ttinh y = 22.8!2x - 0,374 (trong dd x la OD. > la khoi lugng khd) va R - = 0,972 (Hinh 1). '
Hinh 1: Pbmmg trinh tntmg M i:
quan giua OD vd khoi Iirgvg |- - __
kho cua tao S. plateitsis ~
ir - 0 «•:
Phircmg phdp xac dinh khd ndng sinh truang:
Lay mdu tao de do mat do quang (OD) 2 ngav ldn. Khdi lugng khd cua tao sau dd duac tinh loan dua vao cdng thuc y = 22.812x - 0.374.
Phucmg phdp phdn tich ham luang protein vd lipid:
D I phan ti'ch lam lugng protein \ a lipid, cdc mlu tao dugc thu tai pha can bang, khi tao dat sinh khdi cue dai d nga\ nudi thu 8.
Cac mau tao dugc tach ly lam khdi mdi ttudna nudi bdng may ly tdm cd tdc do quay 7.500* vdng/phut uong Ihdi gian 10 phiit. su duns may V tdm Hereaus Supraftige 22. Mau
Optical Drasirr
tao sau dd dugc say khd d nhiet do 55"C trong 2 gid. luu giii d nhiet do am 20°C trudc khi thuc hien cac phan tich hda sinh. Ham lugng lipid trong mau tao khd dugc pban tich theo phuang phdp cua Bligh va Dyer (1959) su dung bdn hgp tach chiet chua chloroform va methanol vdi tj Ie the ti'ch la 2 : I. Khoang 120 ml cua hon hgp na\" dugc su dung de tdch chiet mdi gam tdo khd. Cdc chdt rin dugc phan tach mdt each can than bSng each su dung giay lgc chu) en dung 2 Idp cua Nhat Ban. Cdc chdt hda tan vd dung mdi dugc lam bay hoi ttong may hut chan khdng d nhiet do 60°C. Qua trinh tdch chiet dugc thuc hien 3 ldn cho den khi thu dugc toan bg lugng lipid thd trong mdu tao.
Protein thd dugc phan rich bang phuang phap
Tap chi Khoa hgc Tnr&ng Dgi hoc Can Tha Phdn B. Ndng nghiep Hnn- san ^ a Cong nghi Smh hgc 26 P013): IS(>-187 Kjeldahl (AOAC. 1998). Qua Uinh phan tich
dugc liln hanh tai Vien Cdng nghe Sinh hgc va Mdi trudng, Trudng Dai hgc Nha Trang.
Qudn ly cdc yeu to moi truang:
Cac ylu tfi mdi trudng dugc xac dinh hang ngay. pH dugc do bdng may do pH (Hanna pH Meter, do chinh xac 0,1). Do man dugc do bdng khue xa k l (Refractometer, do chinh xac 0,5%o).
Phucmg phdp xu ly so lieu:
Cac sd lieu sau khi thu thap dugc phan tich bang phep phdn tich phuang sai mdt yeu td (ANOVA) tten phdn mim SPSS 16.0. Khi cd su khdc biet giua cdc gia tri trung binh ve sinh khdi cue dai hay ham lugng protein va lipid cua cac nghiem thuc, phep kiem dinh Duncan's Test dugc su dung de xac djnh su khdc biet cd y nghTa thdng ke vdi muc y nghTa p < 0,05 (Zar, 1999). Tdt ca cac sd lieu ttong --- 6.18 mg/l - ^ 1Z35 mg/l - * - 1 8 . 5 3
thi nghiem dugc trinh bay dudi dang Trung binh (Mean) ± Sai sd chuan (SE).
3 K E T QUA VA T H A O LUAN 3.1 Anh hudng cua nitor len sinh t r u d n g
Kit qua nghien cuu cho thay cac muc nito khac nhau cd anh hudng ro ret len sinh trudng cua quan the tao S. platensis. (J tat ca cdc nghiem thiic, sinh khdi cue dai deu dat dugc d ngdy nudi thu 8 va thdi gian duy tri quan the keo dai 12 - 14 ngay. Trong dd, tao dugc nudi d cdc muc nita cao hon (18,53; 24,7 vd 30,88 mg/l) cho sinh khoi cue dai Idn ban (4,90 ± 0,12; 4,79 ± 0,11 va 4,35 ± 0,28 g/L) so vdi cac muc nito thap ban (6,18 va 12,35 mg/l) (3,06 ± 0.27 va 3,46 ± 0,04 g/L) (p < 0,05). Tuy nhien, khdng cd su khac biet thdng ke ve sinh khoi cue dai dat dugc giira cac muc nito 18,53; 24,7 va 30,88 mg/l hay 6-18 va 12,35 mg/l (p > 0,05) (Hinh 2).
mg/I -m- 24.7 m g / l - ^ - 30.88 mg/l
•'<o
1
12
Uinh 2: Anb budng cua nitu lln Mac du khdng cd su khdc biel thdng ke ve sinh khdi cue dai ciia tao S. platensis dat dugc gida cdc muc nita 18.53, 24.7 va 30,88 g/l nhimg cd the nhdn thd; mdt xu hudng chung rang, khi gia tang muc nita, sinh khdi cue dai dat dugc cua tdo (vao ngay nudi thu 8) cd khuynh hudng gidm (p > 0.05). Ngugc lai, d nhdm thdp hon. tao dugc nufii d muc nito 12.35 mg/l cho sinh khoi cue dai cao hon so
sinb ttudng cua tao S. platensis
vdi muc nita 6,18 mg/l (p > 0.05). Ngoai ra, cac muc nito khac nhau ciing anh hudng den thdi gian duy tti sinh khdi do quan the tdo S. platensis. Trong do, tao dugc nudi d muc nito cao han (18.53, 24,7 va 30,88 g/l) cho thdi gian duy tti sinh khdi qudn the lau hon (14 ngay) so vdi nhdm cd muc nito thap hon (12,35 mg/l va 6,18 mg/l) (12 ngay).
Tap chi Kboa hgc Tnr&ng Dai hgc Cdn Tba Phdn B. Ndng nghiep. Thuy san vd Cdng nghi Sinh hoc: 2612013): ISO-IS' Cac muc nito khac nhau dnh hudng Idn
den sinh trudng cua tao ndi chung va tao S. platensis da dugc d l cap trong nhilu nghien cuu. Du thua hay thieu hut nita deu lam gidm sinh trudng, kha nang trao dfii chat, chat lugng dinh dudng ciia nhilu lodi ldo ttong dd cd ldo S platensis (Hu, 2004; Bulul, 2009; Azov va Goldman, 1982; Zhila va ctv., 2005; Pruvost va ctv., 2009). Trong nghien cuu ndy, khi muc nito cao hoac thap ban gia tri tdi uu (18,53 mg/I), qud ttinh quang hgp cua tao vdn dien ra nhimg vdi cudng do thap, sinh khfii tao gia ldng cham va pha cdn bdng keo dai, ddc biel la d muc nita 6,18 mg/l. Ngoai ldm gidm tdc do sinh trudng, nhung quan sat them trong nghien cuu nay cung cho thay, su thilu hut nita cdn gay ra hien lugng tao ua vang va thdi gian tao tan lui nhanh ban so vdi cac muc nito cao hon.
Theo Pauw et al. (1983): nhu cau ve nito ctia tao lam cao hem tao khue va thap ban tao luc. Muc nito thich hgp cho su phdt trien cua tao khue: Chaetoceros gracilis tu 12,41 den 17,41 mg/l, tao C. calcitrans tu 6,69 - 12,69 mg/l va tao luc Tetraselmis sp. phat ttien lot trong khoang ttr 17.36 den 22,36 mg/l [6].
Chinh vi vay, muc nito loi uu (18,53 mg/l) cho sinh trudng cua tao S. platensis trong thi nghiem nay la hoan toan phu hgp vdi xu hudng tren.
2. Anh hirdng ciia nitu Ien ham lugng protein va lipid
Kit qud phdn tich ham lugng protein va
lipid ciia tao S. platensis nudi d cdc muc nita khac nhau cho thay, ham lugng protein \ a lipid cua tao phu thufic chat che vao cdc muc nita cd ttong mdi trudng nudi vdi xu hudng chung la su gia tang cac miic nito ty le thuan vdi ham lugng protein nhung lai ty le nghich vdi hdm Iugng lipid tich luy ttong l l bao. Cu the, d muc nito cao nhat (30,88 mg/l) ham lugng protein dat dugc Id Idn nhat (69,64%) ttong khi ham lugng lipid dat dugc chi la 10.12% khdi lugng kho. Ngugc lai, d mdc nita thdp nhdt (6,18 mg/l), ham lugng lipid dat dugc la cao nhat (13,48%) trong khi lam lugng protein dat dugc chi Id 52,29% khoi lugng khd cua tdo (p < 0,05) (Hinh 3).
Khi xet rieng dnh hudng cua cac muc nito khac nhau len ham lugng protein lich luy cd the nhan thay rang, gia tang muc nito giup gia ldng ham lugng protein lich luy ttong te bao tdo. Ham Iugng protein dat dugc cao nhdt d muc nito 30,88 mg/l va thdp nhat d muc 6,18 mg/l ip < 0,05). Tuy nhien, khfing cd su khac biet ve ham lugng protein thu dugc d cdc muc nito 18,53 va 24.7 mg/l (p > 0,05). Ngugc Iai, ham lugng lipid ttong te bdo tdo lai ty le nghich vdi cdc muc nito cd ttong mdi trudng.
Trong dd, ham lugng lipid dat dugc cao nhat d miic nita 6,18 mg/l (13,48%) va tiidp nhdt d muc nito 30,88 mg/l (10,12%) (p < 0,05).
Tuy nhien, khdng co su khac biet ve hdm luong lipid thu dugc d cdc muc nito 18,53 va 24',7 mg/l (p> 0,05).
iProtein D Lipid
6.18 12.35 18.53 24.7 30.88 Hlim liFcmg nito- (mg/l)
H i n b 3 : A n b h u d n g ciia n i t u len h a m l u g n g protein va lipid cua tao S. platensis Cdc ki' lir a. b,c klidc nhau tren cdc cgl the biin su klidc biel thdng ki(p<0.05)
184
Tgp chi Kboa hgc Tnr&ng Dai hoc Cdn Tha Phdn B. \diig ngbiip. Thuy san \d Cdng nghe Sinh lioc: 26 (2013): 180-187 Anh hudng cua nito den hdm lugng protein
va lipid ciia cac lodi tao ndi chung va ldo S.
platensis ndi rieng da dugc de cap trong nhieu nghien cuu. Nhin chung. thieu hut nito tiong mdi trudng nudi Iam giam ham lugng protein nhung lai lam lang ham lugng lipid lich luy ttong t l bao (Guillard, 1973). Nito la thdnh phdn CO ban cau lao nen cac axil amin va tiep theo la cac phan tu protein ttong te bao. Khi cung cdp ddy du protem. qua trinh sinh tdng hgp protein dugc tang cudng va tao sinh tiirdng nhanh (Sukenik va c/v., 1993). Ngugc lai, thilu hut nito ttong mdi trudng nudi la nguyen nhdn lam gidm sinh khdi vd ham lugng protein trong t l bao tdo (Bulut. 2009; Pruvost va cti'., 2009; De Loura vd ctv., 1986; Piorreck va ctv., 1984). Su gia tang ham lugng protein (52,29 - 69,64%) luong ung vdi su gia tang cac muc nita (6.18 - 30.88 mg'L) uong nghien cuu nay Id phu hgp vdi xu hudng chung cua cdc ket qua nghien ciiu trudc dd.
Tuy nhien, thieu hut nito uong mdi trudng nudi iai Id nguyen nhan lam gia tang ham lugng lipid tich luy trong te bao. Theo Harrison vd ct\K (1990), thieu hut nito ttong mdi trudng nufii la nguyen nhan lam giam ham lugng protein nhung ham lugng lipid lai tang nhe hoac duy ui d mfit t\' le nhat dinh d nhieu loai tao. Tuong tu. thanh phan lipid ttong mdt sd lodi tdo ldng len dang ke khi nudi chiing ttong mdi ttudng thieu nita (Tedesco va Duerr, 1989; Olguin vd cA— 2001; Azov vd Goldman, 1982; Zhila vd ct\\, 2005; De Loura vd ct\:, 1986; Piorreck va cA-.. 1984). Khi gidm 50%
va 100% miic nito so vdi mdi ttudng (172) chudn trong nudi tdo S. platensis, Ulsu va ctv.
(2011) nhdn lha\. ham lugng lipid tang nhe (13,66 \ a 17.05%) ttong khi ham lugng protein giam manh (53,5 \ a 5.6%). Su thieu hut nita Uong mdi trudng nudi la nguyen nhdn lam giam qud ttinh phan chia le bao, ddn din, mdt lugng Idn carbon dugc chuyen sang cho qud trinh tdng hgp lipid thay vi tfing hgp protein vd day chinh la nguyen nhdn gia lang ham lugng lipid ttong dieu kien thieu nito (Sukenik vd ci\-.. 1993). Trong nudi sinh khfii tdo phuc vu san xudt nhien lieu sinh hgc. giam muc nito trong mdi ttudng nudi la mpt trong
nhung bien phap pho bien nham thu dugc hdm lugng ddu cao nhdl (Pruvost vd ctv., 2009;
Piorreck va ctv., 1984; Bulut, 2009; Cifferi va Tiboni, 1985).
Tdm Iai, c6 thi nhan thay rang, tuy theo muc dich nudi tao S. platensis phuc vu cho muc dich thu protein hay lipid va sinh khfii tdo mong dgi ma cd the lua chgn cac muc nita phii hgp. Nhin chung, de dam bdo hieu qua kinh te, tdi uu ham Iugng protein cung nhu lipid thu dugc nhung vdn ddm bao tfic do sinh trudng.
cd ihl lua chpn muc nito 18.53 mg/L cho nuoi loai ldo nay.
4 KET LUAN VA D E X U A T 4.1 K i t luan
Cac muc nito khdc nhau trong mdi trudng nudi cd dnh hudng rd ret len sinh trudng ciia quan the tao S. platensis. Trong dd, tao dugc nudi d cac miic nito cao ban (18,53; 24,7 va 30.88 mg/l) cho sinh khdi cue dai Idn hon (4,90 ± 0 , 1 2 ; 4,79 ± 0,11 va 4,35 ± 0,28 g/L) so vdi cac muc nita thap hon (6,18 va 12,35 mg/l) (3,06 ± 0,27 va 3,46 ± 0,04 g/L) d ngay nudi thu 8.
Cac muc nito khdc nhau cung dnh hudng Idn den ham lugng protein vd lipid cua tao S.
platensis nudi ttong nudc man. Gia tang cdc muc nito ttong mdi truong nudi ldm gia tang hdm Iugng protein (69,64% protein va 10,12%
lipid d muc nito 30,88 mg/l) nhung lam giam ham lugng lipid (52.29% protein va 13,48%
lipid d muc nito 6.18 mg/l) tich liiy ttong t l bao tao.
Muc nita tfit nhdt cho nudi tao S. platensis la 18,53 mg/l nham dat dugc cac gid tri tdi uu ve sinh trudng. ham Iugng protein, lipid va hieu qua kinh te.
4.2 De xuat
Cdn tien hanh cdc nghien ciiu sau ban ve anh hudng ciia cac muc nito khac nhau len thanh phan va ty le cdc axil beo khfing no.
vitamin,... trong t l bao tdo S. platensis nufii trong nudc man.
Tap chi Khoa hgc Tnr&ng Dgt hgc Cdn Tha Plidn B Ndngnghiep. Tliin-san vd Cdng nghi Sinh hgc: 26 (2013) 180-187 Can nghien cuu anh hudng ciia cdc ngufin
nito khac nhau ( N H / , NO3', N O / ) len sinh trudng va thanh phan sinh hda cua tdo 5. platensis nudi trong nudc man.
Can tiep tuc nghien cuu anh hudng cua cac yen id khac nhu ham lugng phdt pho, carbon va ty le giua chung vdi nhau va vdi nito len sinh trudng va thanh phan sinh hda cua ldo S. platensis nufii trong nudc man.
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