KHOA HQC C 6 N 0 N G H |
Sllr DLJIVG VI KHUAlV AXIT LACTIC 5IIVH BACTERIOCIIVI TROIVG IVldi TRUQIVG ISIVOC CHUA D A U PHLJ
VA BA RUOU
Ngd Thi Phuong DungS VQ Tlii Y^n', Hu^nh Xudn Phong'
T6MTAT
Nghidn cuu ndy nhdm mMc dich xdc djnh vi khudn axit lactic (LAB) cd khd nang sinh tdng hpp bacteriocin (chdt di^t vi khudn) tir ngudn nguydn li^u r^ ti^n Id m6i tni6ng nu6c chua ddu phy vd bd mgoi. K^t qua khao sdt trgn 16 ehung LAB da d u ^ phdn Idp tu cdc sdn phdm l£n men vd cdc lo^i men ti£u h6a, c6 13 d6ng th^
hi^n tinh khdng khudn, trong d6 c6 4 d6ng th^ hi$n khd nSng sinh bacteriocin. D6ng Lactobacillus DC213A c6 khd nang sinh bacteriocin m^nh nhdt (du6ng kinh viing khdng khudn cua bacteriocin d^n 22 mm). Anh hudng di^u ki^n sinh bacteriocin nhu ndng d$ gi^ng/ chCing, thdi gian ii, nhi^t d<> u vd thdnh phdn mfli truimg nu6i cdy cua d6ng Lactobacillus DC213A cQng du(?c thir nghi§m. Sinh kh6i vi khudn vd hdm lugng protein dat cao nhdt Idn lu<?t Id 0,4 g/100 ml vd 778,55 ^g/ml b di^u ki^n nhu sau: ndng dO gi^ng ehung log 7 tb/ml, nhi^t d^ li 35"C, thirl gian u 3 ngdy, sii dyng m61 lru6ng nu6c chua ddu phy dugc bd sung 1096 nudc ba ru(?u, 1% pepton vd 1% beef extract (chdt chi^t tir b6). K^t qud sinh khdi vd hdm lugng protein ndy khdc bi^t khdng y nghia so vdi k^t qud dgt dugc trong mdi truimg ddi ehung MRS (De Man, Rogosa and Sharpe).
Tir khda; Bacteriocin, birupu, nudc chua diuphif, vikhuHn axit lactic.
LOATViiND^
Bao quan thuc phdm Id mOt trong nhimg vdn d^
quan trpng hang ddu cho ngdnh cong nghidp thye phdm. Su xdm nhap ciia nhimg vi khuan c6 h?i khdng nhiing ldm hu hong vd giam chdt lupng thuc pham md con gay nguy hi^m cho nguoi Mt\i dung.
Trong nhi^u flidp ky qua, mpt trong nhiing nguydn nhdn chinh gay ngo dpc thiic phdm do nhung y^u td trong tir nhidn gdy ra chinh Id su c6 mdt cua nhung vi smh vat gay hai. B&n c ^ do, v l ^ su dung khdng sinh trong bao quan thye p h ^ s6 anh huong kh6ng tdt ddn siic khoe con ngudi, vi thd v i ^ tdng cudng an todn thuc pham ciing nhu gidm tdc hai cua phy gia hoa hpc dd tra Ihanh nhu cdu c^p thidt (Kesarcodi- Watson etal., 2{X)8). Dd cung chinh Id ly do hi^n nay ngudi tieu diing rdt quan tdm ddn v i ^ su dyng nhung sdn phim cd ngudn gdc ty nhien khong c6 h?ii cho con ngudi vd mdi trudng.
Vi khudn axit lactic (LAB) Id h$ vi smh vdt ddc trung vd tinh khdng khudn vd an todn cho thi^c phdm, tr6n thd gidi chiing dupc su dung nhu chdt bao qudn tu nhidn. Bdn c^uih dd, bacteriocin, mdt hpp chdt sinh ra tu LAB trong qud trinh sinh truong, dap ling tat ca nhiing ydu cdu cdn tfaidt trong bao quan thtrc pham vd khong ddc hai cho con ngudi vd
' Vi?n NC&PT Cdng ngh| Sinh hpc, Trudng D^i hpc C4n Thcf
mdi trudng, \a thd bacteriocin dang cd khuynh hudng dupc ling dung ldm chdt bao quan thuc pham.
Nudc chua ddu phy vd bd rupu hidn nay la hai phd pham dupc xem nhu Id chat thai ldm d nhilm mdi trudng nudc. Tuy nhidn. ngudn phd pham nj^
chiia nhidu thdnh phdn dinh dudng thudn lpi cho vi khudn phdt tridn. Mdt sd nghidn ciiu tren ttid gidi da sii dyng bd bia nhu mdt ngudn cung cap yeast extract (chdt chidt tir ndm men bia) re tidn trong san xudt bacteriocin (WoIf-Hall et al., 2009). Vi v|y, nghidn ciiu nay dupc thuc hidn nhdm tan dung nhiing ngudn phd thai ndy cho nghidn ciiu san xuat bacteriocin, khdng nhiing gdp phdn han chd mdt phdn nudc thai cd h^i ddn mdi trudng, md cdn ti^t kidm dupc chi phi cho nghidn ciiu khoa hpc va san xuit
LV^TU^IVA PHUONG PHAP 1. Nguyto v$t lidu vd hda chit
- Vi khuin: 16 chiing vi khuin axit lactic dupc phdn Idp tir cdc sdn p h i m Idn men vd cac chd phim men tidu hda dgng ddng khd (Lactominplus, Bioacimin, Zincibio, Antibio, Frobio va Probaclil). Vi khuin Bacillus subtilis dupc phan Idp tu men tiSu hda Biosubtyl II dupc sii dyng ldm ddng ddi khdng-
- Nguydn Udu: nudc chua dau phy vd bd rucu dupc thu thdp trdn dja bdn TP. Cdn Tha.
KHOA HOC CdNG N G H l
- Hda chat: pepton vd beef extract (Merck), glucoza (An Dd), hda chit trong phuong phdp do Bradford,...
- Mdi dudng: mdi trudng nudc mdm, mdi trudng MRS (De Man, Rogosa and Sharpe; Merck) vd MRS broth (Merck).
2. Kidm tra khd ndng sinh bacteriocin cda cdc ddng vi khuin axit lactic
a. Phuong phip kidm tra kha ning khing khuin ehung
Vi khuan LAB dupc nudi trong 5 ml mdi trudng MRS broth a SO^C trong 16 gid. Cho 10 ^1 djch vi khuan trdn mdi trudng MRS aga. Mdi ddng vi khuan tao thanh mpt didm trdn bd mdt mdi trudng.
De khd va u trong 18 gid a 30"C. Tidp theo, trdng ddu 5 ml dich vi khuan Bacillus subtilis bd sung 1%
aga Idn trdn bd mdt dia da u vi khuin trudc dd, dd khd vd li d 30''C trong 48 gid (Hernandez et al., 2004). Thi nghidm dupc thye hidn 3 Idn Idp lai.
Quan sat vdng khdng khuin hinh thanh xung quanh khuan Igc LAB.
b. Phuong phip kidm tra kha ning sinh bacteriocin
Vi khuan LAB dupc tdng sinh khdi trong dng nghidm chiia 2 ml mdi trudng MRS nudc xuyt a 30°C trong 16 gid. Ly tdm d 8.000 vdng trong 20 phiit, lay phan dich trong phia trdn vd chinh pH cua dung dich ve 6,5 bang NaOH O.IN. Nhd 80 ^il dich ly tdm vao gidng tren mdi trudng nudc mdm aga dupc trdn 10%
v/v dich huyen phii ciia Bacillus subtihs, trdnh khdng de dung djch trdn ra ngoai. Moi gidng mot ddng vi khuin, lap Iai 3 Ian. Dd dung dich khd, ii d nhiet do phdng trong 24 gid (Hernandez et al., 2004).
Quan sdt vd do kich thudc vdng khdng khuin. Tir dd, chpn ddng vi khuan cd vdng bacteriocin va vdng khang khuan cao n h i t dd thye hidn thi nghidm tidp theo.
3. Khao sdt anh hudng cua n6ng dd gidng chimg ChuIn bi gidng chiing bdng nuoc mudi sinh ly vd triing a cdc miic dd 6, 7, 8, 9 va 10 log tb/ml.
Chiing 1 ml dung djch chiia vi khuan a timg ndng dd vao 99 ml mdi trudng nudc chua ba ddu da dupc chuIn bi Ouong td bdo vi khuin trong dung dich lan lupt Id 4, 5, 6, 7 vd 8 log tb/ml). U d 30°C trong 3 ngdy. Thi nghidm dupc bd tri nghi nhidn vdi 3 Idn Idp IEII. Chi tidu theo ddi: ^ n g sd vi khuin dupc xdc dinh
bdng phuong phap dem trdn budng ddm hong cau.
Ham lupng protein tdng dupc xdc dinh bdng phuong phap Bradford.
4. Khao sdt dnh hudng ciia thdi gian vd nhidt dd u Chung 1 ml vi khuin (vdi mat sd cho sinh khdi cao nhat d thi nghidm d-dn) vdo 99 ml moi trudng hon hpp nudc chua ddu phu dd dupc chuIn hi. Thi nghidm dupc bd tri dang luy thira 2 nhan td, 4 miic dp vd 3 lan lap Iai. Tdng sd nghidm thiK Id 16. Cdc miic nhidt do lan lupt Id 25, 30, 35 vd 40"C vdi cac thdi gian ii trong 2, 3, 4 vd 5 ngdy. Phan tich ham lupng protein tong vd xdc dinh sinh khdi d cdc ngdy ii.
5. Khdo sdt dnh hudng cua thdnh phdn mdi trudng nudi ciy
Thdnh phan mdi trudng dupc khao sat vdi 7 nghidm thirc: mdi trudng nudc chua dau phu (Huynh Thi Ydn Ly et al., 2009), mdi trudng nudc ba rupu (Wolf-Hall etal., 2009), mdi trudng hdn hpp bd rupu vd nudc chua dau phu vdi ty Id 10, 20, 30 vd 40% va mdi trudng ddi chiing MRS nudc xuyt (Merck).
Chiing 1 ml dung dich vi khuin vdo 99 ml mdi trudng duoc bd sung vdi thdnh phdn dinh dudng nhu tren.
Thi nghiem dupc bd tri 1 nhdn td la thdnh phan mdi trudng, 7 miic dd va 3 lan lap lai. Phdn tich ket qua bang each xdc dinh sinh khdi vd ham lupng protein tdng.
6. Phuong phdp phdn tich vd xu ly sd lidu - Hdm lupng protein tong: su dung phuong phdp do Bradford.
- Xac dinh sinh khdi vi khuin: ly tdm mau d 7.000 vdng/phiit trong 15 phiit vd say d 105°C cho den khi trpng lupng khdng ddi.
- Phuong phdp xir ly sd heu: xu ly thdng kd bang chuong trinh Stagraphics Plus version 5.0 (Manugistics Inc., Rock-ville, USA).
• . K E T QUA VA THAO LUAN
1. Kha ndng sinh bacteriocin ciia cdc ddng vi khuin LAB
Kdt qua kidm tra kha ndng khdng khuin va kha ndng sinh bacteriocin ciia 16 dong vi khuan dupc trinh bdy trong bang 1. Hlu hdt cac ddng LAB deu cd kha ndng khdng khuin, ddng DC213A cd dudng kinh vdng khdng khuan ehung Idn nhat Id 18 mm, ddng thap nhat Id N4rl4-CLAB1.1 (7,0 mm) nhung vdn dat d miic khang khuan trung binh. Kha ndng khdng khuan eiia cac ddng LAB Id do axit lactic, H2O2,
NONG NGHIEP VA PHAT TRIEN N 6 N G THON - KY 2 - THANG 6/2012 57
KHOA HQC CbNG NGHt
baeteriocm, reuterin, reuterieyclin, axit 2-pyrrolidon- 5-eaeboxylic vd mdt sd ehat khdc dupc sinh ra trong qud trinh nudi vi khuin (Ouwehand etal., 2004). Cdc chat ndy gdy lie chd sy phdt tridn eiia vi khuin B.
subtihs. Ba ddng CLAB3.3, CLAB2, N3-15-CLAB3.3 khdng cd tinh khdng B. subtihs, cd thd khd ndng sinh axit lactic eua ehung ydu.
Bdng 1. Khd ndng sinh bacteriocin vd khdng khuin cua 16 ddng vi khuin
STT
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
T^n d6ng vi k h u ^ CLAB4 CLAB3.3 N4-26-23.4-CLAB4 CLAB2 N4-14-CLAB 1.1 N3-15-CLAB3.3 N3-26<;LAB1 N9-26-23.4-CLAB4 CLAB3.4 DC213A DC213 DC2114 DC2113 SC123 Ka KC32
Vung kh^ng khu^n ehung (mm)
10 11 7 15 11 12 18 11 14 9 10 8 11
Viing khing khuin cua bacteriocin (mm)
-•
22 12 7 14
2- Anh Inn'mt' cua non^j dO giong ehung den siah klioi vi khuan va ham Iirc/ng protein
\\i\ qu.i i> hiiih I chn thay sinh klioi dong vi kluian I)C'2i:!A liiEig dan ktii lang nong do giong elnuig. Nong (!(> vi kliuaii tjaii dau la 8 log lb/ml, sau kill nuoi li nong do i-to nhal dat tium' la log 10,03 lb/[iil. Khong <'o sir khac hiel y nghia o do tin cay
!iri% so v<n iV nghiirii thirc n6ng do cluing ban dau la 7 log Ih/iiil, luy nliiiii co khac hiet y nghia so viri cac iighiriii ihirc cnii lai lliiih 2 cho thaV sir anh huong cua iHiiig dl) giong cluing di'U ham lirimg protem long tiling mill Innnig iiiliil cay.
D
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z
0,0}4 log J kig 6 leg 7 kig 8 lug Niint;H; Liiongchurg ni>ml|
Hinh 1. Anh hudng ciia nong dp gidng chiing den sinh khdi vi khuan
dill chu: Cac gii tn cd miu tir giong nhau khac bict killingy nghia iv ni.1t thdng ke \in do tin cay 95%.
Ghi chu: ^^ khdng tao vong khing khuan.
Trong 16 ddng thu nghidm, chi cd 4 ddng DC213A, DC213, DC2113 vd DC2114 Id cd kha ndng sinh bacteriocin. T i t ca cdc ddng sinh bacteriocin ddu cd tinh khdng khuan nhung khdng phdi ddng ndo khdng khuin ddu sinh bacteriocin do tinh khdng eiia LAB sinh ra bdi khdng chi bacteriocin md edn bdi axit lactic, H202, diaxetyl,... Ddng LAB sinh bacteriocin manh nhat eung Id ddng DC213A vdi dudng kinh vdng khdng khuin Id 22 mm. Mdc dii bacteriocin ciia LAB sinh ra gdm nhidu lo?ii bacteriocin khac nhau va phy thupe vao timg lodi LAB nhung eung tiiy thude vdo ddng ehi thj ma chiing cd bieu hi^n hay khdng. Ddi vdi ddng chi thi la B. subtilis thi ehi cd 4 ddng DC2113, DC2114, DC213A, DC213 bidu hidn hoat tinh eua bacteriocin.
Kdt qua cho thay ddng DC213A cd kha ndng khdng khuin tir bacteriocin tdt nhat eung nhu cd kha ndng khdng khuan ehung cao nhat ndn dupc chpn ti thye hidn b thi nghidm tidp theo.
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Hinh 2. Anh hudng ciia nong dp gidng chiing d^n ham lupng protein
Ghi chii: Cic gia tri co mau tir giong nhau kIi3C bid! khdng y nghia ve mit thdng ke vai do tin cay 95%.
Ham krpng protein tdng trong dung dich nuoi cay tang dan khi nong dp gidng ehung tang. D'^^
nay phu h()p vdi nhieu nghien ciiu trutic day la ham
KHOA Hpc CbNO NGHt
upng bacteriocin sinh ra ty Id thudn vdi sy tdng rudng cua LAB (De Vuyst etal., 1996; Mataragas et il., 2004 ). Lupng gidng chiing ban dau Id 7 log tb/ml :ho kdt qua eao nhat vd khdng khdc bidt y nghia vdi long dp gidng chiing la 6 log va 8 log tb/ml. Kdt qua ldm lupng protein sinh ra til ndng dd gidng ehung idy cd su khdc bidt y nghia d dO tin cdy 95% so vdi nghidm thiie gidng ehung Id 4 log vd 5 log tb/ml (Hinh 2).
Tir ket qua ddm tdng sd vi khuin cung nhu kdt qua phdn tich ham lupng protein cho thiy nong dd gidng chiing ban dau Id 7 log tb/ml Id thich hpp.
Lupng protein tdng trong dung dich nudi vi khuin cao nhat cung cd thd kdt ludn Id hdm lupng bacteriocin dupc sinh ra cung cao hon.
3. Anh hudng cua thdi gian vd nhidt dd ii ddn sinh khdi vi khuin vd hdm lupng protein
Sy tdng trudng cua LAB ty Id thuan vdi tdng nhiet dd nudi u, tuy nhien nhidt dd tdng eao cung sd lie chd sy phat trien cua chiing. Kdt qua d hinh 3 cho thay nhidt dp u 35"C eho sinh khdi vi khuin cao nhit, dat 0,46 g/100 ml va khdng khdc bidt y nghia so vdi miie nhidt dp u 30''C nhung cd khde bidt y nghia a miic y nghia 5% so vdi nghidm thiic 25 vd 40°C. Vi vdy SS^C Id nhidt dp tdi uu eho vi khuin phat trien dupe chpn cho cdc thii nghidm tidp theo de xdc dinh sinh khdi va hdm lupng protein dat eao nhat Tuy nhidn kdt qua nay eung cho thiy khoang nhidt dp 30 - 35''C tuong duong vdi dieu kidn nhidt dp mdi trudng viing DBSCL nen cd the giam dupc chi phi eho vide didu chinh nhiet dp trong qud trinh nudi cay vi khuan.
0.5 -] 0,46 a 0.4
1"
1-
0,10.42 a
0.36 0.37
23 30 35 40 Nh^et do (°C)
Hinh 3. Anh hudng cua nhidt dd ddn sinh khdi vi khuin
Ghi chu: Cic gii tri cd miu tu gidng nhau khac bidt khdng y nghia ve mit thdng kd vdi dd tin ciy
Kdt qua nay cung phii hpp vdi nhidu nghidn cim trudc ddy, vi khuin axit lactic cd khd ndng phdt trien vd sinh bacteriocin trong khoang tir 30 ddn 37"C (Gulahmadov etal., 2006). Nghidn ciiu cua Sharma vd edng su (2010) eung eho thiy 35"C Id nhidt dd tdi uu dd tdng sinh khdi vd sinh bacteriocin cua Lactococcus lactis trdn mdi trudng MRS bidn ddi.
Kdt qud anh hudng eua nhidt dd u ddn hdm lupng protein dupc trinh bdy a hinh 4.
Hdm lupng protein tdng trong dung dich phu thudc vdo rlt nhidu ydu td nhu nhi^t dd, pH vd ea enzym cua vi khuan sinh ra trong qud trinh Idn men.
Hinh 4 cho thiy nhidt dO 35 vd 40"C eho hdm lupng protein tdng eao hon, khdc bidt cd y nghia so vdi d 25 vd 30"C. Nhu vgy nhidt dd trong khoang 3 5 - 40"C Id nhidt dp de ddng vi khuan DC213A sinh bacteriocin tdt nhit. Mdt sd nghidn ciiu eung eho thay d 35''C hoat tinh ciia bacteriocin dat dupc cao nhit (Pal et al., 2010; Sharma etal., 2010). Tir dd cho thay nhidt dp u d 35"C vira cho sinh khdi vi khuin cao ddng thdi cung tao dieu kidn sinh bacteriocin thdng qua ham lupng protein tdng tdt nhat
Hinh 4. Anh hudng cua nhidt dd ddn hdm lupng protein
Ghi chu: Cic gii tiri cd miu tii gidng nhau khic bidt khdng 3^ nghia ve mit thdng kd vdi dd tin c$y 95%.
Kdt qua anh hudng ciia flidi gian li ddn sinh khdi khd vi khuin dupc trinh bay d hinh 5. Sinh khdi vi khuin tdng tir ngay ii thii 2 ddn ngay thii 3 vd sau dd ed khuynh hudng giam nhung vin ehua cd sy khde bidt d ngay thii 4 va thii 5 so vdi ngdy ii diii 3. Sinh khdi vi khuin d ca 3 ngay nay ddu cao hon va khde bidt y nghia so vdi ngdy ii thii 2. Didu nay cho thay sinh khdi vi khuin eao nhat d ngdy thii 3 va khdng tdng niia, cd thd la do gidi han vd mdt dinh dudng cua mdi trudng nudi cay. Do dd, ddi vdi mdi tnrdng
N6NG NGHIEP VA PHAT TRIEN N 6 N G TH6N - KY 2 - THANG 6/2012 59
KHOA HOC C 6 N G N G H |
thii nghidm nay thi 3 ngdy Id thdi gian nudi ii thich hpp dd thu dupc sinh khdi vi khuin tdt nhit.
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Hinh 5. Anh hudng cua thdi gian ii ddn sinh khdi vi khuin
Ghichii: Cicgii tii cd miu ti/gidng nhau khic bidt khdng y nghia vd mit thdng kd vdi d^ tin c$y
trinh ii eung nhu hdm lupng protein tdng cho th^
thdi gian nudi vi thieh hpp Id 3 ngdy, vira cd thd ni ngdn thdi gian nudi li vtra ddm bao hdm lupnj protein khdng gidm.
Sy tuong tde giiia nhidt dd vd thdi gian nudi i!
ddn sinh khdi vl khuin dupc trinh bay d hinh 7. FKl qud eho thiy b 35"C vd thdi gian nudi ii 3 ngdy die kdt qud sinh khdi vi khuin cao n h i t Ngodi ra, vfi didu kidn nhidt ddi nhu d nudc ta nhidt dd trung binh tuong ddi cao ndn vide chpn nhi^t dO nudi u 35°C cung rlt phii hpp vdi didu kidn nhidt dO ty nhidn^
cd thd tidt kidm chi phi eho vide dam bao nhidt dp nudi ii.
'i ^^ 1 --1
TWj\ gian (ngiy)
Hinh 6. Anh huong cua thdi gian u d^n hdm lu^ng protein
Ghi chii: Cic gia tri cd mau tiigiSng nhau khic biet khdng y nghia v4 mit thdng kd vdidd tin c$y 9S%.
Hinh 6 cho lhay anh huong ciia thdi gian u d^n ham lu()ng protein trong m6i Uirong nuoi cSly. Him luong protein tang trong 2 - 3 ngay diu nhung sau do giam ro r^t vi khic bi^t c6 -j nghia o dO tin cjy 95SI sau 4 - 5 ngay u, Nghi6n ciiu cua Ogunbanwo vi cong su (2003) vk anh huong cua di^u ki^n nuoi cS(y den kha nSng san xuat bacteriocin cua vi khuSn Lactobacillus brevis cho thay thdi gian u vi khuin khoang 48 - 60 gio cho ham luqmg bacteriocin cao n h i t Vi«c giam ham lugng protein tong a ngay nuoi tl thii 4 v4 5 14 do nguon dinh duOng vi k h u i i sir dung da can ki6t, bacteriocin cQng &k bi b i & tinh vi CO ban chat la protein, nhat la khi nuoi u 6 nhiSt do cao. Nhu vay, to Vit qua v^ mjt sd vi khuSn sau qua
Tlieri gian (ngiy)
Hinh 7. Anh hu6ng cua nhi^t dO vd th6i gian t i ^ sinh khdi vi khudn
Hinh 8 cho thSy sir kA h(>p giua nhiM do va thS gian nudi u d^n ham lui^ng protein tdng, d nhiet dp 40°C sau 2 ngay cd gid tit cao x&iit nhung khdng'co khdc biSt nhi4u so vdi d 35°C sau 3 ngdy nudi li. Voi muc dich vua d?t sinh khdi cao vua san xuit dirge bacteriocin vdi hdm lupng cao nen chpn thdi gian w nhi^t dp nudi u thich hpp Id 3 ngdy d35°C.
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5Hinh 8. Anh hudng ciia nhidt dd vd thdi gian th.
hdm lupng protein
4. Anh hudng cAa thdnh phin mdi trudng audi ely ddn sinh khdi vi k h u l a vd hdm lupng protein
KHOA HOC CdHG N G H |
Thi nghiem ndy thue hien nudi ii ddng vi khuin DC213A trdn 7 loai mdi trudng, trong dd MRS la mdi trudng chuydn biet dd ddi chiing. Cac mdi ti-udng thu nghiem la nudc chua ddu phy (Huynh Thi Ydn Ly et al, 2009), nudc bd rupu (Wolf-Hall et al, 2009), hdn hpij nudc chua ddu phu : bd rupu (ty Id 9:1; 8:2; 7:3 va 6:4) cd bd sung thdm 1% beef extract vd 1% pepton.
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MRS Hcmnifu NUIK HH 10 111120 IIIIJO IIIMO
hu Thanh phan
Hinh 9. Anh hudng eiia thdnh phan mdi trudng ddn sinh khdi vi khuan
Ghi chii: Cac gia tri cd miu ti/gidng nhau khic biet khdng y nghia vemitthdngke vdidd tin cay 95%.
Hinh 9 cho thay mdi trudng nudc chua dau phu cung nhu bd rupu la mdi trudng khdng thudn lpi dc ' ddng vi khuan thu nghiem phdt trien tAng sinh khdi.
" Tuy nhien sy phdi hpp cua 2 mdi trudng nay cung nhu i' viec bd sung them 1% beef extract vd 1% pepton eho
• thay vi khuin phdt trien rat tdt va lupng smh khdi thu
• dupc khdc bidt khdng y nghia vdi mdi trudng ddi
• chiing MRS (0,4 g/100 ml). Cdc ty Id phdi hop giiia nudc chua ddu phu va hem rupu eho kdt qua khdng khac biet y nghia d dp tin cay 95% va cQng khdng khdc biet vdi mdi trudng MRS.
; Ket qua tir hinh 10 cho thiy mdi trudng hdn hpp '. nudc chua dau phu vd ba rucoi (9:1) cd ham lupng protein cao nhat, dat 778,55 ng/ml vd khdng khdc bidt y nghia so vdi mdi trudng ddi chiing MRS (812,22 ng/ral). Tuy nhidn d ty Id phdi chd ndy l$i cd .' khac bidt y nghia so vdi tat ea cae nghidm thiic edn i 1^. L^ do cd the trong ba rupu cd nhidu loai protein khdc ngodi yeast extract ma vi khuan khdng the sir
•' dung dupc ti ehuyen hda thanh bacteriocin cung if nhu cd the nhiing chat khde cd tdc dung iie chd ndn
khi tdng hdm lupng ba rupu trong mdi trudng thi gia tri protein lai thap hon. Mdi trudng nudc chua ddu ' phu vd bd rupu do khdng bd sung nhirng dudng chat
can diidt nhu beef extract vd pepton nen ham luong bacteriocin va protein tdng khdng cao. Tir cac ket qua tren, hdn hpp mdi tiirdng ciia nuoc chua ddu phu va ba ruou d ty Id phdi chd 9:1 va cd bd sung thdm 1%
pepton va 1% beef extract la mdi trudng thich hpp de tang sinh khdi cung nhu dat dupc hdm lupng protein cao nhat khi nudi li vdi ddng vi khuan thii nghidm.
Thanh phan
Hinh 10. Anh hudng cua thdnh phdn mdi trudng ddn hdm lupng protein
Ghi chu: Cac gia tried miu tii gidng nhau khic bietklidngynghia vemittlidngke vdidd tin ciy 95%
Tom lai, mat s6 gidng chiing la log 7 tb/ml, u a 35"C trong 3 ngay vdi mdi trudng nudc ciiua dau phu bd sung them 10% ba rupu, 1% pepton va 1% beef extract cho kdt qua sinh khdi cung nhu ham lupng protein cao nhat.
IV. KET LUAN
Trong tdng sd 16 ddng vi khuan LAB dupc khao sat cd 13 ddng cd tinh khdng kliuan va trong dd chi cd 4 ddng cd kha nang sinh bacteriocin. Ddng vi khuin DC213A cd kha ndng khang khuan vd sinh bacteriocin manh nhat vdi dudng kinh viing khdng khuan Id 22 mm. Cdc dieu kien nudi ii de dat dupc ndng dp vi khuan cung nhu ham lupng protein cao:
ndng dp gidng chiing ban dau la log 7 te bdo/ml, nhidt dp u 35"C va thdi gian ii la 3 ngdy. Mdi trudng nudi cay Id hon hpp ciia nudc chua ddu phy vd ba rupu vdi ty Id 9:1 (bo sung 1% beef extract va 1%
pepton) cho sinh khdi 0,4 g/100 ml cung nhu ham lu(7ng protein 778.55 jig/ml cao nhat vd khdc biet khdng ^ nghia so vdi khi nudi cay trong mdi trudng ddi chiing MRS.
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PRODUCTION OF BACTERIOCIN BY LACTIC ACID BACTERIA IN TOFU SOUR UQUID AND BREWER'S GRAINS
Ngo Thi Phuong Dung, Vu Thi Yen, Huynh Xuan Phong Summary
This study was carried out to determine lactic acid bacteria (LAB) having bacteriocin producing ability firom tofu sour liquid and brewer's grains media. A total of 16 LAB strains was isolated and screened for bacteriocin production. There were 13 strains performing their antimicrobial activities and of which, 4 strains were able to produce bacteriocin. Strain Lactobacillus DC213A was remarked with the significantly highest antibacterial activity based on bacteriocin zone diameters (22 mm). Effects of conditions for bacteriocin production by Lactobacillus DC213A such as inoculation level, incubation time, incubation temperature and culture medium, were also examined. The significantly highest levels of biomass and protein at 0.4 g/100 ml and 778.55 jig/ml, respectively, were obtained in conditions as below: inoculation level 7 log cells/ml, incubation temperature 35''C, incubation time 3 days, a medium of tofii sour liquid added with 10% brewer's grains, 1% peptone and 1% beef extract. These levels of biomass and protein had no significant difference to compared with the results in the treatment of usmg the control MRS medium (De Man, Rogosa and Sharpe).
Keywords: Bacteriocin, lactic acid bacteria, tofu sour liquid, brewer's grains.
Ngudi phan bidn: TS. T r i n Thf Mai Ngay nhdn bdi: 27/2/2012 Ngdy thdng qua phan bi^n: 2/5/2012 Ngdy duy^t ddng: 10/5/2012
