KHOA H p c C d N G N G H l
SLT DUIMG ACETOBACTEH THOXB SAIM X U A T THACH DIJA
Ngd T^ii Phuong Dung', L6 Tlii Lin\ H u ^ Xudn Phong'
T6MTAT
Thach dira hay cdn gpi Uk Nata-de Coco la logi thiic 5n khi phd bi^n a nhidu nudc tr^n thd gi6i cung nhu o Vi?t Nam. DSy la mdt san phdm ldn men tir nudc dira nhd vi khudn Acetobacter xylinum, gdm th^h phdn chii ydu la xenluloza. Nghifin ciiu nay dugc thpc hi^n nhdm xac djnh nhimg ddng vi khudn Acetobactercb kha nang ldn men th^ch dira \k khio sdt didu ki^n l^n men iinh hudng ddn sij tdng hpp xenluloza. T6ng sd vi sinh v§t hidu khi trong 3 mdu djch l^n men din;^: thu thSp tir co sd san xudt b Bdn Tre trong khoang 8,92 - 9,14 log CFU/ml. Bay ddng vi khudn dupe phftn I§p \k djnh danh ddu thudc gidng Acetobacterd\fa fr6n die diem khudn lgc, hinh dang va cAc dSc tinh sinh hda. Khudn l?c c6 d ^ g hinh trdn va mau ving nh^t T^ bdo vi khudn c6 dgng hinh que, gram Sni, catalaza duong tinh. tgo v6ng halo sing trfin m6i trudng YPGD b6 sung 0.596 CaCOj va 4% ethanol, chuydn mau mdi truing tir xanh sang vAng khi c6 b6 sung bromocresol green. Ddng Acetobacter N c6 thi tgo ra luting xenluloza cao nhdt. Kdt qua thir nghidm cdc di^u ki^n Ifin men cho thdy lupng xenluloza cao nhdt dupe tgo ra trong qui trinh Ifin men Id khi su dyng nudc dira da dugc ii I6n men tu nhiSn 60 giP. nong d6 gidng chiing ban d^u la 6 log tb/ml, hdm lui^ng dudng ban ddu phii hop cho qud trinh Ifin men la S'biix vd chi cdn bd sung diamon photphat (DAP) v6i Ldu lupng thdp (0,2%).
Tir kh6a: Acetobacter, xenluloza vi khudn, l^n men, nudc dira. th^ch dua.
LDATVANDE
Thach dira hay edn gpi Id Nata^e Coco Id loai thuc an kha phd bidn 6 nhidu nirdc fren thd gioi cung nhu b Viet Nam. Ddy la mOt san pham len men tir nudc dira kho nhdf vi khuan Acetobacter xylinum, thanh phdn chii yeu Id xenluloza (Budhiono et al., 1999). San pham nay Id loai thtrc pham khdng chua nhieu dinh dudng, it nSng lupng, ham lupng chat xo cao vdi ban chdt hoa hpc Id poUsacarit ndn rat tdt cho hd tidu hod, chdng dupe bdnh beo phi, kich thich nhu ddng rudt giup didu hod bai tidt tdt hon,...
Xenluloza tir vi khuan hay mdng xenluloza smh hpe duoc ling dung vdo nhidu linh vvrc khdc nhau nhu frong sdn xudt gidy. frong y hpc dd ldm mdng sinh hpc tri bdng vd tdn tiiuong da,... Ddi vdi Iinh vuc thyc pham, ngoai iing dung dd sdn xudt thach dCra, mdng xenluloza sinh hpc cdn dupe iing dung ldm mdng bao xiic xieh, mdng bao quan dua tuoi thay cho hda chat,... Hidn tai cung da cd nhidu nghidn ciiu vd xenluloza sinh hpc va trong tuong lai ddy vdn Id dd tdi dd nhidu nhd khoa hpc nghidn cuu vi nhQng ling di^ng mdi cua nd.
Hidn nay, van dd dang dupe quan tam 6 Vi^t Nam cung nhu cdc nudc frdng dira vd sdn xuat cdc
' Vi?n NC&PT Cdng ngh? Sinh hpc, Trirdng Dgi hpc Cdn Tho
san phdm tir dira frdn thd gidi ndi chung vd cdc nha may com dira nao sdy ndi ridng. dd Id lupng nudc dira hang nam thai ra rat ldn. Day la mdt frong nhung nguydn nhan gay d nhidm mdi trudng ndu khong dupe tan dung va xit ly. Trong giai doan dira khd, nudc dira chira nhidu dinh dirdng nhung khd sii dung de lam thiic an hay nudc udng. Vide tdn dung nudc dira khd vdo san xudt Id nhu cau cdp thidt khdng nhimg giai quydt van dd mdi trudng md cdn lam tang gid tri sii dyng ciia dira.
Bdn Tre Id tinh cd didn tich frdng dira lon nhdt ca nudc vd day ciing la noi cd nhidu co so chd bien thach dira. Tuy nhi^n, hdu nhu tat cd cdc co so noi day ddu sdn xudt b quy mo ndng hp nho. Quy trinh san xuat chii ydu dua vdo kinh nghidm cua mdi gia dinh vd cd su khdc nhau vd ngudn gidng su dung, da sd tdi str dung l^i ngudn gidng sau khi da len men nhidu ldn. Do dd chdt lupng ldm ra khdng ddng ddu, khdng dn djnh vd nang sudt thdp. Nhidu nghidn ciiu gdn day cho thdy vide sii dung ngudn gidng tiiudn chiing vd t^ Id bd sung cdc thdnh phdn vdo frong qud trinh san xudt cdc sdn phdm I6n men ndi chung va thach dira ndi ridng ddng mpt vai frd rdt quan frpng, anh hudng ddn nang suat vd chat lupng san pham.
Ndi dung nghidn ciiu ndy gdm phdn lap, djnh danh so bd, tuydn chpn gidng Acetobacter thuan vd khao sdt cdc ydu td frong qud trinh ldn men tdng hpp xenluloza smh hpc c6 nang sudt cao vd dn djnh.
NONG NGHliP VA PHAT TRIEN NONG T H 6 N - KV 2 - THANG 7/2012 57
KHOA HQC C d N G N G H t
I . VAT UEUVA PHUONG PHAP 1. Nguydn vdt U§u vd hda chdt
- Gidng Acetobacter N (Vi^n NC&PT Cdng nghd Sinh hpc, Trudng D?d hpc Cdn Tho).
- Nguydn li^u: djch l^n men th^ch dira tai co so sdn xuat d Bdn Tre. nudc dira khd.
- Hda chdt: Glucoza. DAP (diamdn photiihat.
(NH^jHPOJ. SA (sunphat amdn (NHJ^SO^).
CaCOa, axit axdtic, yeast exfract, glyxerin. ethanol.
pepton, bromocresol green,..
- Mdi tiirdng YPGD (Saeki et al., 1997): yeast exfract (5 g/l). polypepton (5 g/l). glyxeril (5 g/l) vd D-glucoza (5 g/l); PCA (Plate Count Agar. Merck).
2. Phan ldp vd djnh danh so bO vi khudn Acetobactert\i6\ch l6n men th?ich dira
Xac dinh tdng sd vi sinb vit hid'u khi trong djch len men thach rfua.Tdng sd vi sinh vM hidu khi frong dich len men thach dira dupe xdc djnh frdn mdi trudng PCA, l?p Iai 3 ldn. U d 30"C vd ddm sd khudn lac sau 24, 48 va 72 gid. Chpn cdc dia cd sd khuan lae tir 25 ddn 250 dd tinh kdt qua.
Phan lip va dinh danh so- bd cic ddng vi khudn Acetobacter. Vi khuan Acetobacter duoc phdn lap frdn mdi truong nuoc dira khd (DAP 2 g/l, SA 8 g/l.
glucoza 10 g/l. aga 40 g/l, nudc dira khd da \x 24 gio bd stmg vira dii 1000 ml) (Nguydn Tliiiy Huong vd Pham Thdnh Hd, 2003). Dinh danh so bd vi khudn bang cdch nhudm gram, thii catalaza, cdy chuydn fren mdi trudng YPGD bd sung 0,5% CaCOj vd 4%
ethanol, thu kha nang oxy hda lactat thdnh CO2 vd H2O fren mdi trudng YPGD bd sung bromocresol green 0,02%.
3. So sdnh vd tuydn chpn ddng vi khudn Acetobacter So sinh kha ning phit trien cUa cic ddng vi khuan Acetobacter: Cac ddng vi khuan phan ldp ciing vdi ddng Acetobacter N dupe nudi tang sinh khdi frong binh tam gidc chira mdi trudng nudc dira cr 30°C frong 24 gid. Xdc djnh m^t sd vd chiing vdi cimg ndng dp gidng ban ddu la 6 log td bao/ml (log tb/ml) vao cdc bmh tam gidc 250 ml chiia 100 ml mdi trudng ldn men. U ldc 150 vdng/phiit 0 30°C. Sau 24 gid-, xac dinh mdt sd td bao bdng phuong phap ddm true tidp frdn budng ddm Burk-Tifrk dd so sdnh muc dp phdt tnen a i a cdc dong vi khuan.
So sinh kha ning Idn men thach cua cic ddng vi khuan Acetobacter: Tidn hdnh ldn men vdi cae ddng vi khuan cd ndng dp gidng chung ban ddu la 7 log tb/ml frong cde khay nhua (17,3 x 13,0 x 7,3 cm)
chiia 300 ml nu^n: dira dupe ii frong 24 gid va di^
chinh vd 5"brix. Quan sdt su hinh thanh thach trong cdc khay ddn khi trong khay khdng cdn djch I6n men (khodng 5 - 1 0 ngdy) dd tdng hpp xenluloza niia thi kdt tiiuc thi nghidm vd chpn tiidi gian ldn men cho tdt cd cdc thi nghidm tidp theo.
4. Khdo sdt dnh hudng ciia tiidi gian li nudc din ddn si; hinh thdnh xenluloza
Nudc dira dupe u ldn men tu nhidn a nhi^t dg phdng. Sau 24, 36. 48. 60 vd 72 gid ii. tidn hdnh phoi chd. didu chinh mdi tnrong vd 5" brix bdng glucoza va chiing gidng vdi ndng dp 7 log tb/ml). Su dung mau nudc dira chua dupe u vd phdi chd Idm ddi chiing.
5. Khdo sdt dnh hudng a i a ndng dd vi khudn Acetobacter
Thi nghidm dupe thuc hidn vdi dong Acetobacter^^ vd thdi gian u nudc dira chpn lpc diroc tir thi nghidm frdn. dp brix moi trudng dupe di^
chinh vd 5" brix. Chiing gidng vdi ndng dp vi khudn ban ddu ldn lupt Id 3, 4, 5,6 va 7 log ti)/m].
6. Khdo sdt dnh huong cua hdm lupng duimg ban ddu
Sit dung kdt qud va thuc hipn tuong tu nhu cac thi nghidm fr^n, didu chinh dp brix vd 5,6, 7.8,9,10 va 11° brix bdng duong glucoza. Ddi chiing la mSu nudc dira vdi dp brix tu nhidn (4''brix).
7. Khdo sdt dnh hudng ciia hdm lupng DAPvd SA bd sung
Bd sung DAP va SA vdi ty 1$ dua theo cdng thiic mdi hotdTig san xuat thgch dira ciia Nguydn TTiiiy Huong va Phgm Thanh Hd (2003). Cac ty Id bo sung nhu sau: 0.2% DAP va 0,8% SA; 0.2% DAP vd 0,896 SA vd khdng bd sung cd DAP vd SA.
8. Phuong phdp phdn tich
DO brix trudc va sau ldn men dugc xdc dinh bang brix kd, pH xdc djnh bang pH kd. Khdi lui?ng tiigch (xenluloza) hinh tiidnh dupe frai ddu fren khay cd gidy tiiam khd nudc vd sau dd xdc djnh bdng cich cdn frpng lupng. Sd Udu dupe xtr ly thdng kd b ^ chuang trinh Stagraphics Plus version 5.0 (Manugistics Inc., Rock-ville, U S ^ .
• . K E T QUA THAO LUAN
1. Phan ldp vd djnh danh s o bO vi khui"
Aceti>bactertii dich Ito men t h ^ h dita Tdng sd vi sinh vdt hidu khi frong cdc mdu dich Idn men t h ^ h dira thu thdp tir cac co sd sdn xuat c Bdn Tre cd m4t so frong khoang 8,92 - 9,14 U 58 N 6 N G NGHllP VA PHAT TRIEN N 6 N G T H 6 N - KY 2 - THANG 7/201^
KHOA HQC C 6 N G NGHt
CFU/ml (Bang 1). Tdng vi sinh vat hidu khi tir cdc mdu phan tich tai cdc c o sd cao hon nhidu so vdi kdt qua eiia tac gia Nguydn Thuy Huong va Pham Thdnh Hd (2003), mat sd td bdo vi khudn Acetobacer xylinum sau 6 ngdy nudi cay chi dao dpng frong khoang 7,51 - 7,68 log tb/ml. Didu nay cd thd giai thich la do bi nhidm vi sinh vdt hidu khi khdc ngodi Acetobacter xylinum frong qud frinh san xudt.
Bang 1. Tdng sd vi sinh vdt hidu khi frong djch ldn men th<ieh dua
Mau A B C
C a s a Tran Phuoc
Mai Thi PhuQnjr Trdn Van
Chi^n
Tdng so vi sinh vat hi^u khi floR CFU/ml)'
8,92 9,14 9,05
Gbi chii: 'Cic sd hdu trong bing Ii trung binh ciia ba Ian lip lai
Khuan lac cdc ddng vi khuan phan lap ddu cd dang hinh frdn, nhd vd mau vang nhat. Khuan lac ciia cac ddng Al, B2, C3 cdn cd mang nhay xung quanh.
Td bao cdc ddng vi khuan phan lap duoc khi quan sdt dudi kinh hien vi ddu cd dang hinh que. Tuy nhidn, qua quan sat edc ddng A2 vd C2 ed ehidu dai td bdo ngdn hon cdc ddng Al, Bl, B2, C l vd C3. Ket qua kiem fra sinh hda cho thay cdc ddng vi khuan nay deu CO catalaza duong, gram am, tao duoc vdng halo sang fren mdi hudng YPGD cd bd sung 0,5% CaCOj va 4%
ethanol. chuydn mau mdi tnrdng YPGD cd bd sung bromocresol green frr xanh sang vang va ngupc lai.
Do dd. cd 7 ddng vi khuan nay dupe dinh danh so bd thudc gidng Acetobacter (Sudsakda et al., 2007;
Kaderel etal.. 2008; Moryadee vd Patiiom-Aree, 2008).
2. So sdnh vd tuydn chpn ddng vi khudn
Hinh 1. Mdt sd cdc ddng vi khudn Acetobacter sau 24 gid Ito men
Gbi chu: Cic sd lieu bidu thi tidn cac CQt trong bieu dd Ii gii tii tiling binh cUa 3 Ian Up Iai. Cic gii tii cd cimg ky tu the hi$n su khac bi$t khdng c6 y nghia thdngke add tin ciy 95%.
Trudc khi tidn hanh chimg gidng ldn men thach, 7 ddng vi khudn phan lap dupe cimg 1 ddng Acetobacter^ dupe nudi ldc vdi cimg ndng dp gidng ban ddu Id 6 log tb/ml frong cdc binh tam gidc dd so sdnh muc dp phdt fridn. Sau 24 gid ii ldc d 150 vdng/phiit, mat sd 7 ddng vi khudn ddu dat 8 log tb/ml. Ddng Acetobacter N dat mat sd cao nhat vd khdc bidt cd y nghia thdng kd d miic 5% vdi tdt ca cdc ddng cdn lai (Hinh 1).
Kdt qua quan sdt sir hinh thdnh xenluloza cho thay d ngay thir 6 dich ldn men trong cdc khay cua mpt sd ddng cdn rdt it hoSc djch ldn men hdu nhu khdng cdn niia. Do dd, thdi gian kdt thiic ldn men 6 ngdy dupe chpn cho cdc thi nghidm tidp theo. Tir 300 ml nudc dira (da u d 24 gid) dupe phdi chd vd pH 4,5 bdng axit axdtic va bd sung glucoza dat 5° brix, ndng dp gidng chiing ban dau Id 7 log tb/ml thi 5 ddng vi khuan N, Al, B2, Cl va C3 cd khd nang tao xenluloza vdi khdi lupng frdn 200 g. Kdt qua thdng kd d dp tin cay 95% cho thay khdi lupng xenluloza do eac ddng ndy tdng hpp khac bi^t khdng cd y nghia (Hinh 2).
Hmh 2. Khdi lupng xenluloza (g/300 ml) khi ldn men vdi cdc ddng vi khudn
Ghi chd. Cic sdlidu bieu thj trdn cac cdt trong bidu dd la gii tq trung binh cua 3 Ian lip lai- Cic gia trj cd ciing ky tu thd hidn su khic biet khdng cd y nghia tiidng kd add tin ciy 95%.
Vd mdu sdc, xenluloza do ddng Acetobacter N tdng hpp cd mdu sdc frdng hon so vdi edc ddng cdn lai. Dd chd bidn dupe san phdm thach dira tiing, d?p thi mdu sdc khdi xenluloza sau I6n men ciing ddng mdt vai frd rat quan frpng. Day Id rapt frong nhung tidu chudn dd nha tiiu mua lua chpn. Ngodi ra, kdt qua vd sir phdt tridn cua cac ddng vi khuan sau 24 gid len men (Hinh 1) cho tiiay ddng Acetobacter}^ dat mat sd cao nhat, khdc bidt cd y nghia thdng kd d mite 5% vdi cdc ddng cdn lai. Vdi tdc dd tang m?t sd nhu vdy khi ldn men sd han chd dupe sir xam nhidm cua cdc vi sinh vdt khdc, hidu qua ldn men se tdt hon. Nhu vdy,
N6NG NGHIEP VA PHAT TRIEN NONG T H 6 N - KY 2 • THANG 7/2012 59
KHOA HQC C 6 N G N G H |
ddng Acetobacter N Id ddng tdt nhdt dupe chpn cho cde thi nghidm tidp theo.
3. Anh hirdng ciia thdi gian ii nudc dira ddn si/
hinh thdnh xenluloza
Nudc dira dupe li d cdc khoang thdi gian 24, 36.
48, 60 vd 72 gid trudc khi tidn hdnh phdi chd vd 5"
brix, pH 4.5 vd chimg gidng vdi ndng dO ban ddu Id 7 log tb/ml. Tat ca cdc nghidm thuc dui,K li d nhidt dd phdng (28 - 32°C). Kdt qud sau 6 ngdy ldn men cho thdy khdi lupng xenluloza tang tir nghidm thiic nudc dira khdng dupe li ddn nudc dira dupe u d 60 gid tiii dat lirpng xenluloza cao nhdt, khdc bidt cd y nghia thdng kd vdi cdc nghidm thirc edn lgi (Hinh 3). Tuy nhidn. nudc dira sau 72 gid ii cd khdi lupng xenluloza giam xudng do nudc dira ii cdng iSu, hdm lupng dinh dudng gidm ddn. hdm lupng glucoza cung gidm ndn hidu qua tdng hpp xenluloza cung gidm.
i"
a » 1 JJL • il
• -"
ii 11 1 1
cd gidm nhung hidu qud Idn men khdng eao so v6i nudc dira u sau 60 gid.
4. Anh hudng ciia ndng dd vi khudn Acetobacto ddn sv hinh thdnh xenluloza
Mdi frudng nudc dira ldn men dupe didu chinh vd 5** brbt vd pH vd 4,5 vdi ndng dd gidng chung ban ddu ldn lupt Id 3, 4, 5, 6 vd 7 log tb/ml. Tuong t^thi nghidm frdn, dd brix khdng cd su thay ddi nhi^u so vdi ban ddu. Sau 6 ngdy Ito men, khdi lupng xenluloza tang ddn khi ndng dd chung cdng cao v^
d^t khdi lupng cao nhdt khi mdt sd vi khudn Id 6 log tb/ml. Kdt qud thdng kd cho thdy vdi ndng dd 6vA7 log tb/ml thi khdi lirpng xenluloza dupe tdng hpp cao nhdt vd khdng cd sir khdc bidt nhung khdc bi^t y nghia so vdi cdc ndng dO cdn lai (Hinh 4). Chpn ndng dd gidng chung ban ddu Id 6 log tb/ml se cd lpi hon vi vira tidt kidm dupe gidng vao san xuat vira dl dang nhan gidng dd dat dupe m^t sd.
Hinh 3. Khdi lupng xenluloza (g/300 ml) khi ldn men vdi nudc dira da qua li Gbi chu: Cac sd Udu bieu thi ti^n cic cdt trong bieu dd Ii gii tri trung binh cua 3 Ian lip Iai. Cic gii tried ciing ky tu thd hien si/khic bidt khdng cd y nghia thdng kd add tin ciy 95%.
Sir kdt hpp giiia axit axdtic vd ngudn cdc bon ciing cd anh hudng ddn hidu qua ldn men. Vdi ngudn cac bon Id glucoza, bd sung axit axdtic lam tang hidu qua ldn men nhung hidu qua ldn men se giam ddi vdi ngudn cdc bon Id sucroza (Toda etal., 1997). Trong giai doan phdi chd vdi mdu ddi chiing nudc dira chua qua ldn men tij nhidn sinh ra axit, ham lupng dirdng chii ydu la sucroza, can nhidu axit axdtic dd didu chinh vd pH 4,5; Id pH thich hpp cho vi khudn Aceti}bactsr phdt trien vd smh xenluloza. Nhu v^y, nudc dira u cang Idu thi ham lupng sucroza cdng giam do su chuydn hda thdnh glucosza. khi pH mdi trudng cang giam, hdm lupng axit axdtic bd sung vdo cang it, xenluloza dupe tdng hpp cdng nhidu. Do dd.
dd brix sau ldn men vdi nudc dira da u 24, 36, 48 gid
Hinh 4. St; thay ddi xenluloza d cdc ndng d$
chiing gidng
Gbi chu: Cic sd hdu bidu thi ti^ cic c^
troag bidu dd la gii tri tiung binh cua 3 Ian lip Iai. Cic gii tii cd Cling ky tir thd hidn $if khic bi^t khdng cd y ngbia thdng kd add ttii ciy 95%.
5. Anh hudng ciia hdm lirpng dudng ban ddu d&
s\f hinh thdnh xenluloza
Diing glucoza dd didu chinh dp brix ldn IM ^ 5, 6, 7. 8, 9, 10 vd 11 (dd brix hr nhidn cua nudc diS sau khi dd li tir nhidn la 4° brix). Sau 6 ngay ldn men, d khay 5" brix d^t dupe khdi lupng xenluloza cao nhat va khdc bi^t cd y nghia thdng kd so vdi cdc m*
dp cdn 1^ d miic y nghia 5% (Hinh 5). Mjc du glucoza Id CO chdt dd hinh thanh xenluloza nhung khi hdm lupng glucoza qud cao thi khdi lupnS xenluloza cd khuynh hitdng giam do glucoza ngoi dupe chuydn hda thanh xenluloza cdn dugc chiQP hda thdnh axit gluconic. Lupng axit gluconic tich ty ngay cdng nhidu se lam giam pH xudng thdp hon so
60 NONG NGHllP VA PHAT TRIEN N 6 N G THON - KY 2 - THANG 7/2012
KHOA H p c C d N G N G H l
vdi miic pH tdi thich eho vi khuan Acetobacter phit trien de tao xenluloza (Embuseado etal., 1994).
khdc. Khi bd sung ca DAP va SA thi hidu qua len men cao nhat. Tuy nhidn. kdt qua ciing cho thay khi chi bd sung DAP (0,2%) cung dat dupe kdt qua khdc bidt khdng cd y nghia d dp tin cay 95% vdi nghiem tiiirc khi bd sung cd DAP vd SA (0,2% va 0,8%).
Hinh 5. Su thay ddi xenluloza do dnh hudng cOa do brix ban ddu
Ghi cbti: Cic sd Udu bidu tbi tren cic cdt trong bidu dd li gii tri trung binh cua 3 lin lip Iai- Cic gii tri cd cimg ky tu thd hidn su khic bidt khdng cd y ngbia thdngke add tin cay 95%.
Vdi dp bnx ban dau ldn hon 5, pH mdi trudng sau len men giam ddn thdp hon 4,0. Masaokavd cdng su (1992) chirng minh neu ham lupng dudng bd sung vdo mdi trudng ban ddu qua cao, lupng axit gluconic sinh ra nhieu nen hieu qua tdng hpp xenluloza cung giam. Tuy nhien. vdi mdi trudng d 4 va 5" brix, pH sau len men lai cd su tang nhe. Theo Toda va cdng su (1997), ham lupng axit gluconic frong qua binh len men se tang vd sau dd se giam frd lai, theo dd pH mdi trudng ban ddu giam ciing se tang frd lai.
Masaoka va cdng su (1992) cung cho rang axit gluconic cdn duoc chuydn hda thdnh chat khac frong qua trinh len men. Nhu vdy, vdi mdi tnrdng d 4 vd 5"
brix, ham luong dudng khdng cao ndn lupng axit gluconic tieh tu khdng nhidu va ciing da nhanh chdng chuydn hda thanh chdt khdc. Do dd, lupng dudng ban ddu 5° brix, khdi lupng xenluloza dupe tdng hpp nhidu nhat, hdm lupng dudng ban dau khdng cao se trdnh dupe su tich tu axit gluconic va ldm vang mdi trudng khi ndu, ngoai ra cdn tidt kidm dupe chi phi bo sung glucoza vdo san xuat. Id ILH chpn ^ t nhdt dd tidn hdnh len men.
6. Anh hudng ciia DAP vd SA bd sung ddn s\f hmh thdnh xenluloza
DAP vd SA cdn dupe bd sung dd eung cap thdm ngudn dinh dirdng, ngudn nito cho vi khudn su dung dd chuyen hda thanh xenluloza. Ddi vdi nudc dira da ii khdng bd sung hda chdt se ldn men khdng hidu qua so vdi nudc dira cd bd sung hda chdt (Hmh 6), chiing td ngodi ngudn dinh dudng frong nudc dira vd glucoza bd sung, ddng vi khuan Acetiybacternky ddi hoi phai bd sung tiiem mot sd ngudn dmh dudng
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Hinh 6. Sv thay ddi khdi lupng xenluloza do dnh hudng ciia DAP vd SA bd sung Ghi chii: Cic sd lidu bidu thj trdn cic cdt trong bieu do li gii tri trung binh cda 3 lan lip lai. Cac gia tr/ CO Cling ky tu thd hidn su khic biet khdng cd y nghia thdng kd add tin ciy95%.
Khi khdng bd sung SA va DAP se thidu ngudn dinh dudng bd sung, ddng vi khudn nay se su dung glucoza de tdng hpp xenluloza Id chinh. Su thay ddi dp brix sau ldn men vdi nude dira chi bd sung 0,2%
DAP vd 0,8% SA chiing td ddng vi khuan ddi hdi cung cap ca ngudn nito dinh dudng vd ngudn sunfat thi hidu qua len men se cao hon. Ket qua nghien ciiu khdng bd sung SA. ehi cdn bd sung 0,2% DAP cho kdt qua ldn men van hidu qua cao rat cd y nghia, vira tidt kidm dupe chi phi su dung hda chat, vd mdt an todn sinh hpc eung ban chd dupe hda chat frong thuc phdm.
IV. KfT LUAN
Bay ddng vi khudn Acetiibacter^Si dupe phan Up ti: 3 mau djch ldn men th^ch dira dupe tiiu tiiap tgi 3 eo sd san xudt d Bdn Tre. Tdng sd vi sinh vgt hidu khi dupe xde djnh frong khoang 8.92 - 9,14 log CFU/ml. Ca 7 ddng ddu cd chung dac didm vd hinh dang khuan lac la cd mdu vdng nhat. hinh frdn, nhd va mpt sd ddng cd mdng nhay xung quanh. Ca 7 ddng vi khuan phan Igp dupe cd dang hinh que ddi vd que ngdn. Tat ca cde ddng ddu la vi khuan gram am, catalaza duong tinh, tao vdng halo sdng fren mdi trudng YPGD bd sung 0,5% CaCOj va 4% etiianol, chuyen mdu mdi trudng bd sung bromocresol green tiJ xanh sang vdng va ngupc lgi. Kdt qua cho tiiay ddng AcetijbacterN khi ldn men dat mat sd vd tdng hpp xenluloza cao, thach cd mdu sdc frdng hon. Cac
N 6 N G M'=»'PP V A PHAT TPIFN M A N G THAN - K\' 2 • THANG 7/2012 61
KHOA HOC C 6 N G NGHt
didu ki?n thich hpp de ddng vi khudn Acetobacter N tdng hpp xenluloza: nudc dim dupe u lu nhidn trong 60 gid. phdi chd dat 5" brbc bang glucoza, ndng do gidng chiing ban ddu Id 6 log tb/ml. ldn men 6 ngdy d nhiet dd phdng (28 - 32°C). bd sung 0.2% DAP vd khdng can bd sung SA vdo mdi InnVng ldn men.
Ldi cdm on: Car tic gia chin tiianh cam on Trudng Dai hoc Can Tlur da hd ti\y nipt iihiii kinh phi tbiic bidn tid nghiem. Cim on Clnrong tiinb Trpng didm Cluhi A (fSPSNRCT A.-^ian Core Program) di bio dicu kien de cbimg tdi tham gia Hpi tiiio ACP vi bio cio vd kdt qua nghien cuu luiy.
TAI 14U THAM KHAO
1. Budhiono. A . B. Rosidi, H. Talier and M.
Iguchi, 1^)99. Kinetic aspects of bacterial cellulose formation in nata-de<oco culture system Carbohydrate Polymers 40. pp. 137-143.
2. Embuseado, M. E.. J. S. Marks and J. N.
BeMiller. 1994. Factors affecting the production of cellulose by Acetobacter xylinum. Food HydrocoUoids 8, pp. 407418.
3. Kaderel, T. T , T. Miyamoto. R. K Oniango, P. M. Kutimal and S. M. Njoroge. 2008. Isolation and Identification of the Genera Acetobacter and Gluconobacter in Coconut Toddy (mnazO- African Joumal of Biotechnology 7. pp. 2963-2971.
4. Masaoka, S., T. Ohe and N. Sakota. 1992.
Production of Cellulose from Glucose by Acetohactei xylinum. Joumal of Fermentation and Bioengineering 75, pp. 18-22.
5. Moryadee, A and W. Patiiom-Aree, 2008, Isolation of Thermo tolerant Acetic Acid Bacteria from Fruit for Vinegar Production, Research Journal of Microbiology 3 (3), pp. 209-212.
6. Nguydn Thiiy Huong vd Pham Thdnh Hd, 2003.
Chpn lpc ddng Acetobacter xylinum tiiich hpp cho cdc I091 mdi tnrdng dung frong san xuat xenluloza vi khudn vdl quy md Itm. Tap chi Di truydn hpc va Ung dpng. Hpl Di fruydn hpc Vi<*t Nam 3, fr. 49.
7. Saeki. A , G. Thceragool, K. Matsushita. H.
Toyama, N. Lotong. and O. Adachi. 1997.
Development of Thermotolerant Acetic Acid Bacteria Useful for Vmegar Fermentation at High Temperatures. Bioscicnce, Biotechnology, and Biochcmistiy 61 (1). pp. 138-145.
8. Sudsakda. S.. W. Snchareon and W. Pathom- Aree, 2007. Comparision of Three Enrichment Broths for the Isolation of Thermotolerant Acetic Acid Bacteria from Flowers and Fruits. Research Joumal of Microbiology 2(10), pp. 792-795.
9. Toda. K.. T. Asakura, M. Fukaya, E. Entani and Y. Kawamura, 1997. Cellulose Production by Acetic Acid-Resistant Acetobacter xylinum. Joumal of Fermentation and Bioengineering 84. pp. 228-231.
USING ACETOBACTESFOR PRODUCTION OF NATA - DE COCO
Ngo Thi Phuong Dung, Le Thi Lin, Huynh Xuan Phong Summary
Nata-de Coco is one kind of popular foods that have been consumed world-wide and in Vietnam as well. It is fermented product from coconut juice by a role of Acetobacter xylinum, including cellulose as an essential component in the final product This research was carried out to investigate the cellulose producing Acetobacter slrains and the effect of fermentaUon conditions on their cellulose production. Total aerobic microorganisms in 3 samples of nata fermenting medium collected at local producers in Ben Tre was in the range of 8.92 - 9 14 log CFU/ml. Seven bacterial strains were isolated and identified as belonged to Acetobacter genus based on the morphology examinations and biochemical charactenstics. The bacterial colony had round form with lightly yellow colour. These bactenal strains were gram negative, rod. catalase positive, giving bnght halo zone in YPGD medium supplemented with 0.5% CaCOj and 4%
ethanol. converting medium colour from green to yellow when supplemented bromocresol green. Strain Acetobacter N was found to give the highest yield of cellulose production. By testing the fermentation conditions for cellulose production, the results showed that the highest cellulose level was achieved when produced with conditions as below: use of coconut liquid medium that was naturally fermented 60 hours before, level of inoculation at 6 log cells/ml. the initial adding sugar content at 5° brix and level of adding diamonium hydrogen phosphate (DAP) at 0.296.
Key words: Acetobacter, bacterial cellulose, coconut Juice, fermentation, nata-de coco.
Ngudi phan bidn: TS. TVdn Thi Mai Ngdy nh$n bdi: 30/3/2012 Ngdy tiidng qua phdn bidn: 28/6/2012 Ngdy duy^t dang: 5/7/2012
62 NONG NGHIEP VA PHAT TRIEN NONG T H 6 N - KY 2 - THANG 7/2012
