Tqp chi khoa hgc TrUdng Bqi hpc Quy Nhdn - Sd'2, Tqp IX nam 2015
SJj HINH THANH CAU Tl/ TAO HlJCfNG TlT QUA TRINH LEN MEN CO DINH HlJOfNG KHOI HAT CA PHE NGUYEN VO
DE SAN X U A ' T C A PHE NHAN
TA CHI D 6 N G LUAN% LE THI LIEN THANH", LE VAN HOANG^
1. GlCfl THIEU
Ca phe la mdt loai thffc uong mau den cd chffa cha't caffein va cd nguon gdc tff ca phe nhan dffdc rang xay thanh bdt. Theo trang tff dien Wikipedia (2009), vao t h e k i thff IX, nhffng ngffdi dan thudc bd lae Kaffa (thudc Ethiopia ngay nay) da phat hien ra mdt loai eay ed la mau xanh t h i m , hoa trang, qua chin cd mau do giong qua anh dao. Hp da diing nffdc ep cua qua eay nay lam thffc ud'ng va cam nhan dffdc sif tinh tao. Ngay nay, eSy ea phd dffde trong tai hdn 50 qud'c gia trdn the' gidi va da trd thanh mdt Ioai thffc udng thdng dung tren toan eau [I].
Tai Viet Nam, vao nam 1857, cac nha t r u y i n dao cdng giao da dffa cay ca phe vao trong thff nghiem d Bd' Traeh (Quang Binh) va Quang Tri. Nhffng mai de'n nam 1870, cay ca phe mdi dffde dffa ve trong d Ha Nam Ninh va sau dd (tff nam 1888 de'n nam 1913) dffdc tiong d a i tra tai cac d i n d i i n cua Phap d Nghe An, Ha TTnh, Quang Tri, Thanh Hda. Dd'n nhffng nam 1920-1925, khi khai pha vung da't bazan mau md thudc eac tinh Tay Nguyen, ngffdi Phap da dffa cay ca phe vao trong tien nhffng vung da't nay va dSy ed t h i dffdc xem la thdi diem quan tipng nha't danh da'u bffdc khdi dau eho sff phat triin cua mot loai cay cdng nghiep day tiem nang cua Viet Nam ngay nay, bdi sff thich hdp ve dieu kien tho nhffdng va dieu kien khi hau cua cay ca phe tren viing da't nay [1], [2].
Hien nay, vdi tong dien tich trong cay ca phd tidn toan qud'c khoang 200.000 ha va tong nang sua't ck phe ffdc dat trung binh khoang 250.000 ta'n, Vidt Nam da tid thanh nffdc xua't kha'u ea phe ldn thff hai tren the' gidi, chi sau Brazin [1]. Tuy nhien, gia tri xua't khau ma loai cay cdng nghiep nay mang lai cho nen kinh td' ciia da't nffdc chffa tffdng xffng vdi t i i m nang v l san Iffdng cua nd.
Qua ca phe chin sau thu hoach cd vo ngoai m a u dd. Thanh phan hda h p c cua nhan ea phe h i u nhff khdng cd cac ca'u tu" tao hffdng thdm [3]. Hffdng va sac nau cua ca phe nhan dffdc hinh thanh chu y e u trong tie'n tnnh len men (u) nhd vai trd cua he vi sinh vat tff nhidn (na'm men, na'm mdc va vi khuan) cd san tren b l mat qua ca phe tffdi va dac bidt la trong mdi trffdng da't, trong do, vai trd ciia vi khuan lactic la chii d a o hdn ca [4].
TA CHI DONG LUAN", LE THI LIEN THANH", LE VANHOANG'^
Theo ke't qua khao sat d nhilu vCing trong ca phe cua Vidt Nam, dac biet d cae tinh Miln Trung-Tay Nguyen, qua trinh ehe' bie'n ca phe nhan ap dung cdng nghe tach vo qua, u va phdi sa'y. Do vay da loai ngay tff ban dau phan vd qua vo'n chffa mdt so' thanh phin ed ldi trong qua tiinh tao hffdng cho ea phe nhan [4].
Vi le neu tren, nghien effu hffdng vao viec sff diing mdt sd' gid'ng vi khuan lactic dffdc phan lap, tuyen chpn tff kho'i hat ca phd nguyen vd sau u tff nhien. Tff dd, tie'n hanh boat hda va nudi sinh khd'i chung de tao thanh tac nhan sinh hpc len men khd'i hat ca phe nguyen vd nham sff dung mpt sd' thanh phdn cd ldi cho qua trinh len men eo dinh hffdng, vdi mue dich nang cao hieu qua tao hffdng cho ca phe nhan.
2. NGUYEN LIEU vA P H U Q N G PHAP NGHIEN CCU 2.1. Nguyen li$u
Nghien cffu dffde thffc hien vdi ca phe chin (loai ca phd vd'i-Robusta) thu hai tai huyen Chff-Prdng, tinh Gia Lai-la loai ca phe dffdc tiong phd bie'n va chie'm san Iffdng ldn nha't tai Viet Nam. Qua tnnh phan lap, boat boa cac gid'ng vi khuan lactic cd san trong qua ca phe nguyen lieu de sff dung vao nghien effu dffdc thffe hien tidn mdi trffdng ed ban MRS, la mdi trffdng dinh dffdng nhan tao hoan chinh nha't cho sff sinh trffdng va phat trien sinh khd'i cua vi khuan lactic [5], [6], ed bo sung thanh phan nffdc va vo qua ca phe (15ml/l).
Sff dung hdn hdp 02 gid'ng vi khuan lactic dffdc tuyen chpn tff qua trinh phan lap, nudi ca'y va boat hda neu tien (ed kha nang sinh tong hdp acid lactic va este thdm cao) cho qua trinh Idn men ed dinh hffdng khd'i ca phe hat tffdi. Ti le hdn hdp vi khuan sff dung so vdi khd'i ca phe hat tffdi can len men la 6% (v/w-thi tich sinh khd'i vi khuin lactic, tinh bang mililit/ khd'i Iffdng ca phd hat tffdi, tinh bang gam).
Viec so sanh, danh gia hieu qua cua thffc nghiem dffdc thffe hien tien cd sd phan tich, so sanh cac ca'u tff tao hffdng dffdc hinh thanh ciia ca phd nhan thu dffdc tff thffe nghiem va ca phe nhan thffdng pham (ciing loai Robusta) mua tren thi trffdng.
2.2. Phffdng phap nghidn cffu
De tach cac este thdm tff ca phe nhan thffdng pham va ca phe nhan sau qua trinh len men co dinh hffdng, chiing tdi sff dung phffdng phap chie't soxhlet, vdi dung mdi s^
dung la n-hexane. Nguyen tac eiia phffdng phap la cac ca'u tff va este thdm cd mat trong cac mlu ca phe nhan (da dffdc nghien nhd) la nhffng hdp cha't khdng phan cffc hoac it phan cffc, do vay se hda tan td't trong dung mdi n-hexane (dung mdi khdng phan cffc) nhd qua trinh ngam mlu trong dung mdi va qua tnnh chffng ca't hoi ltfu tren bp ehie't soxhlet [7]. Thdi gian chie't tach tren bd chie't Soxhlet dffde tiiffc hien tff 4h-6h. Dich ehid't thu dffdc sau qua trinh chie't bao gom dung mdi va cac ca'u tuf thdm (ke ca cac este thdm) cd the boa tan trong dung mdi n-hexane.
SU HINH THANH CAU TO TAP HlfONG TLT QUA TRINH LEN MEN 129 Cae mlu dieh ehid't thu dffde sau qua trinh chie't soxhlet cdn chffa nhieu dung mdi
n-hexane, do do gay anh hffdng de'n ke't qua phan tieh can thie't. Chinh vi vay, cae mlu nay dffdc lam "giau" bang phffdng phap cd quay chan khdng trffdc khi tie'n hanh eae thi nghiem dinh danh cac ca'u tff bang phffdng phap sac ki kbi-ghep khd'i pho (GC-MS).
Nguyen tac cua phffdng phap la dffa vao sff khac nhau vl nhiet dp bay hdi giffa dung moi va cac ca'u tff hda tan can ehie't tach de lam giau mau bang each cho bay hdi dung mdi tiong dieu kien ehan khdng [8]. Qua trinh lam giau eac mlu tren thie't bi cd quay ehan khdng dffdc thffe bien cho dd'n khi Iffdng mau cdn lai dat khoang 2 ml so vdi so' Iffdng mlu can lam giau ban diu la 10 ml.
Sff dung sac ky khi ghep khd'i pho GC-MS (Gas Chromatography-Mass Speetiometry) de thu eac phi dl cd lien quan de'n cac ca'u tff tao hffdng cd trong eae mlu ea phe nhan can nghidn cffu (mau 1 va mau 2). Nguyen tac phffdng phap: hdp cha't can phan tieh sau khj qua cdt sac ky (GC) se taeh thanh eac cha't rieng biet (mdi cdt tffdng ffng vdi 1 pie trdn sac dl) va cac chat nay se dffdc nhan dang bang dau dd MS/MS. Dau dd MS/MS boat ddng tien cd che' diing mdt nguon nang Iffdng ldn de pha v5 ca'u tnic phan tff cua cac cha't va tao thanh cac manh ion nhiim dien tich dffdng (+). Mdi chat se tffdng ffng vdi mpt sd' manh ion nha't dinh. Dffa vao sff cd mat ciia cac ion nay, ngffdi ta dinh danh dffde cac cha't cd mat tiong hdp cha't can phan tich. Qua tnnh dinh danh cac ca'u tff dffdc thffc hien bang each so sanh vdi eae manh ion cua mau phan tich vdi cac manh ion cua cha't ehuan da cd san tiong thff vien phd [8], [9]. Vide xac dinh so Iffdng va dinh danh eae ea'u tff tao hffdng tff 2 phd do thu dffde eua mlu 1 va mlu 2 dffdc thffc hien qua ffng dung thff vidn NIST va WATER cd sfn tiong phan mem he thd'ng.
3. KET QUA - THAO LUAN
Tff ket qua phan tich bang phffdng phap sac ki khi - ghep khd'i phd (GC-MS), chung tdi da thu dffdc 2 phd do tffdng ffng ciia mlu ca phe nhan thffdng pham (mlu 1) va mlu ca phd nhan thu dffdc tff thffc nghiem (mlu 2) cd lien quan de'n cae eau tff tao hffdng (Hinh 1 va Hinh 2).
Viec dinh danh cae ca'u tuf dffa vao cac pic xua't hien tren sac k>' do theo mdt sd' nguyen tac [8] bao gom: (1) SiJ dung thff vien ed sfn trong phan mem he thd'ng, bao gom thff vien NIST va WATERS, de thffe hien vide so sanh giffa cae pie thu dffdc trdn sac ky dd vdi thff vien cd san tren he tho'ng; (2) Vide so sanh giffa chat phan tieh vdi thff vien thdng qua so sanh khd'i phd (m/z), do do thdi gian Iffu khdng anh hffdng de'n ke't qua dinh danh; (3) Dp chinh xac cua phep so sanh nay dffdc danh gia thdng qua "dp tffdng thieh", dp tffdng thieh eang cao thi ke't qua dinh danh cang chinh xae. Khi pho khd'i cua mdt cha't phan tich hoan toan gid'ng vdi phd khd'i cua mdt cha't chuan trong thff vien thi dp tffdng thich dffdc bieu thi la 1.000, khi dp tffdng thich cang giam thi mffc dp gid'ng nhau cang dia'p. Dp tffdng thich dat tren 800 dffde xem la cho ket qua cd dp tin cay eao; va (4)
TA CHl DONG LUAN'. LE THI LIEN THANH", L £ VAN HOANG' Dp tffdng thieh cang cao khi mdt pic dffdc tach rieng le tidn sac ky do va khdng bi anh anh hffdng bdi cac pic ian can khac.
Hinh I. Pho do GC-MS cd liin quan den cdu tii tao huong cua mdu 1
^ "" hr Lck
Hinh 2. Pho do GC-MS cd liin quan den cdu td: tao hucfng cua mau Dvfa tren ket qua cia cac pho d6 GC-MS thu dirdc (Hinh 1 va IBnh 2) va thU vien NIST, WATERS, chung toi da xac dinh dilcic 29 cau tft thdm trong mlu 1 (Bang 1) va 36 ca'u ul thdm trong mau 2 (Bang 2).
sif HlNH THANH cXu TLf TAP HUONG TP QUA TRJNH LEN MEN
Bang I. Ket qud dinh danh cdc cdu tvt thcfm til pho do GC-MS Hinh I
TT 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29
Ten hcTp chS't Diphosphoric acid, disooctyl ester (C|gH,gO^P,) Heptane, 2,2,4,6,6-pentamethyl (C,,!!,^) Oxirane, (3.3-dimethylbutyl) (C,H,jO)
Benzene. 1.2-diethyl (C^flJ Tridecane, 3-methyl (C|,H,„)
2-Propenoic acid, 1-methylundecyl ester (Cj^H^gO^) 2-Decenal, (Z) (C,„H|jO)
Benzoic acid. 2-hydroxy-, ethyl ester (CgHi^Oj) 2,4-Decadienal, (E,E) (C,„H|,0)
Benzocycloheptatriene (C|,H|g) 2,4-Decadienal, (E,E) (C|„H,p) Tridecane, 3-methyl (C|jH,g)
lH-Purine-2,6-dione, 3,7-dihydro-l,3,7-trimethyl (C,H„N,0,) 1,2-Benzenedicarboxylic acid, butyl octyl ester (C,pH,pO^) Octadecanoic acid, ethyl ester (C,^H^Oj)
Octadecane, l-(ethenyloxy) (C,uH.,gO) 9-Octadecynoic acid (C^Hj^Oj) E-9-Tetradecenoic acid (C|^H,gO,) Oxirane, [(tetradecy]oxy)methyl] (C,,H^^Oj)
Hexadecanoic acid, 2,3-dihydroxypropyl ester, (.+!-) (Cj^H^gO.,) 9.12-Octadecadienoyl chloride. (Z,Z)-(C„H3,C10) 7-Methyl-Z-tetradecen-l-ol acetate (C^Hj^O, ) 4,7,10,13,16,19-Docosahexaenoic add, methyl ester, (all-Z) (C„H^,Oj) 8,11.14-Eicosatrienoic acid, (Z,Z,Z)- (C,„H„0,) Di-n-octyl phthalate (C„H„0^»)
1-Heptatriacotanol (C„H,jO) Squalene (C,„H,„) Ethyl iso-allocholate (C,jH„0,)
12-Methyl-E,E-2,13-octadecadien-l-ol (C^Hj^O)
Thdi gian lim(s)
6.404 6.921 7.540 7.866 10.148 10.846 11.093 11.262 11.577 11.756 11.936 13.117 21.337 23.59 23.934 25.812 26.925 27.038 27.217 29.242 29.725 30.107 30.535 32.120 33.481 33.931 39.069 45.693 48.459
DO ttftfng thi'ch
904 896 830 865 837 838 922 885 925 908 948 910 916 914 901 878 922 880 842 827 919 892 831 912 917 844 920 834 852
132 TA CHI B O N G LUAN'. L t THI UF.N THAtMH'. LE V AN HOANG' Bdng 2. Ket qud dinh danh cdc cdu tiJC thom td phS do GC-MS Hinh 2
TT 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
Ten hrfp chat Acetic acid (C,Hp,)
Tricyclo [3.2.1.0<2,4>]oct-6-ene.
(1.alpha.,2.alpha..4.alpha..5.alpha.) (C,H,„) Heptane. 2,2,4,6,6-pentamethyl (C„H,J Limonene (Ci^H^^)
Oxirane, phenyl (CjH„0)
2.6-Dimethyl-l,3,5,7-octatetraene.E,E (C,„H„) Phenylethyl Alcohol (C,H,„0 )
Benzoic acid, 2-hydroxy-, methyl ester (CgH^O, ) Acetic acid, hexyl ester (C^H|^0,)
Benzoic acid, 2-hydroxy-, ethyl ester (C^Hi^O, ) Dihydromyrcene (Cn,H|^)
Benzocycloheptatriene (C|,H,^) 2,4-Decadienal, (E,E) C,„H,p Benzocycloheptatriene (Ci.H,^) Tridecane. 3-methyl (C„H,„)
Acetic acid, phenylmethyl ester (C^H|^Oj) 2-Propenoic acid, 3-phenyl-, methyl ester (CIUHKJO^ ) Hexadecanoic acid, methyl ester C|,H,^0,
1.2-Benzenedicarboxyhc acid, butyl 2-ethythexyl ester (C,|,H,^0.,) Phosphorothioic acid, O.O-diethyl 0-(3.5,6-trichloro-2- pyridinyl) ester (C,H,,C1,N0,PS)
Octadecanoic acid, ethyl ester (C,|,H.,„0,)
9.12-Octadecadienoic acid, methyl ester, (E,E) ( C „ H , p , ) Phytol (C,„H„0)
2-Undecanethiol, 2-methyl (C|,H„S) 9-Octadecynoic acid (C,^H„0,) Hexadecanoic acid, ethyl ester (C|gH,p,)
9,12-Octadecadienoyl chloride, (Z,Z) (C,jH„C10) Oleic Acid ( C „ H , p , )
9,12-Octadecadienoic acid (Z,Z) (C„H„0,)
Cholesta-8.24-dien-3-ol. 4-methyl-, (3.beta.,4.alpha.)(C„H„0) Di-n-octyl phthalate (C„H„Oj)
Norethindrone (C,„H,,0,) l-Heptatriacotanol { C „ H , p ) 2.6,10,14,18.22-Tetracosahexaene.
2.6,10,15,19.23-hexamethyl-, (all-E) (C,„HJ
Stigmasta-5,22-diene, 3-methoxy-,(3.beta..22E) (C,„H,„0) Ethyl iso-allocholate (Cj,H„0,)
Th&i gian liAi 4.863 5.427 6.934 7.609 7.856 8.025 8.947 10.172 10.397 11.263 11.578 11.758 11.938 11.994 13.130 15.303 21.281 22.676 23.261 23.598 23.947 25.746 26.105 26.848 26.949 27.511 29.737 30.232 30.108 30.536 33.279 33.628 33.909 39.070 44.681 45.289
DO tiftfng thich
860 861 911 946 880 814 892 818 962 887 830 909 853 860 916 886 907 911 908 828 917 936 840 821 923 851 929 878 883 811 867 806 838 942 878 808
SU HINH THANH CAU Tif TAG Ht/GNG TJJ QUA TRINH LEN MEN 1 ^ Kd't qua thu dffdc tff eae phd dd GC-MS (Hinh 1 va Hinh 2) va viee dinh danh cac
ca'u tff tao hffdng tff 2 pho do nay (Bang 1 va Bang 2) cho tha'y cac ca'u tff tao hffdng cd tiong mlu 1 va mlu 2 dffdc dinh danh vdi dd tin cay kha cao (dp tffdng thich deu dat tren 800). Ben canh do, tren eiing mpt phffdng phap phan tich, ke't qua vl sd'Iffdng ca'u tff tao hffdng cd trong mlu 2 nhieu hdn mlu 1 la 07 ca'u tff (36/ 29). Sff tang len dang ke ca'u tff tao hffdng khi sff dung hon hdp 02 gid'ng vi khuan lactic dffdc phan lap, tuyen chpn theo dinh hffdng sinh tdng hdp td't acid lactic ddng thdi tao dffdc cac ester thdm vdi cac ca'u tff khac. Mat khac, nhd vao sff "ap dao" cua gid'ng vi khu^n lactic sff dung da ban chd' 6i((ic ding ke qua tiinh "len men tap" tao ra eae hdp cha't khdng ed ldi, anh hffdng dd'n hffdng vi eua ea phe nhan.
Ke't qua nay cho phep khang dinh: len men cd dinh hffdng la giai phap tieh cffc lam tang ca'u tff tao hffdng cho ca phe nhan, ddng thdi chffng td eae hdp phan cd tiong vo qua ea phd tffdi da tham gia vao sff hinh thanh ca'u tff thdm cho ca phe nhan sau qua trinh u. Cung tff ke't qua nay, ky vpng cd thd "cdng nghiep boa" phan nao cdng doan len men dffa trdn de xua't mdi la u khd'i hat ca phe nguyen vd bang sinh khd'i vi khu^n lactic tffdng thich.
Rieng mlu 2 cd sff Men dien cua mdt sd'ester cd lien quan dd'n eac acid acetic nhff:
acetic acid hexyl ester, acetic acid phenylmethyl ester,... Cac ca'u tff nay dffdc hinh thanh tiong qua trinh ldn men qua ca phd nguyen vd da chffng td dffdc phin nao vai tio "lam ed cha't" eua vd qua ea phd dd'i vdi sff tang ldn ve Iffdng eua eac ca'u tff tao hffdng cho mau thffe nghidm nay.
Ke't qua dinh danh tien mlu 2 eiing da phat hien them 02 ca'u tff tao hffdng quan trpng dffdc tao thanh ma mau I khdng cd, do la: 2-propenoic acid, 3-phenyl-, methyl ester va hdp chat limonen. Day la mdt ester va mpt hydrocarbon quan trpng trong nhieu hdn hdp hffdng hay tinh dau thffe vat (2-propenoic acid, 3-phenyl-, methyl ester trong hffdng qua dau; limonen la thanh phan chinh tiong tinh dau qua hp citrus) [10].
4. KET LUAN
Vdi eong nghe de xua't: sff dung hdn hdp vi khuan lactic tffdng thich d le 6% (v/w) dffde nudi sinh khd'i trdn mdi trffdng MRS cd bd sung 15 ml/1 nffdc vat tff vd ca phe tffdi de len men (u) khd'i bat ea phe tffdi nguyen vd. Sau 96h u d nhiet dp khd'i hat khoang 45°C da thu dffdc 36 ca'u tff tao hffdng, trong khi do, mau ca phe nhan thffdng pham ciing loai cua Viet Nam chi ehffa 29 ca'u tff tao hffdng trong ciing dieu kien xac dinh.
Ke't qua ban dau kha quan nay se lam nIn cho viec hffdng de'n tao hffdng cho ca phe nhan theo chuan "Ca phe Chdn" ndi tie'ng bang phffdng phap sinh hpc vdi quy md cdng nghiep.
TA C H I B 6 N G L U A N % L E THI U E N THANH", LEVANHOANg TAI LIEU THAM KHAO
[1] httn://vi-wikiDedia.org/wikiC%C3%A0 Dh%C3%AA
[2] Eleanor Jane Steriing, Martha Maud Huriey and Le Due Minh, VietNam: A Natural History, (2000).
[3] Nguyin Van Thoa, Co sd ly thuyet vd sdn xudt thuc pham, Nxb Giao due. Ha Noi, (2006).
[4] Le Hdng Phii, Nguyin Dffe Lffdng, D6 Dai Nghia, Nghiin cdu che tao che pham Biocoffee Aspergillus Niger vd dng dung len men cdc logi cd phi. Tap chi phdt trien KH&CN, tap 11, so' 12-1, (2008).
[5] Ahmed T. and Kanwal R., Biochemical characteristics of lactic acid producing bacteria and preparation of camel milk cheese by using starter culture, Pakistan Vet. Journal 24, (2004).
[6] Bozoglu F., Chirica LC, Yaman O. and Gurakan C , In lactic bacteria. Current Advances in Metabolism, Genetics and Applications, Springer, (1996).
[7] Pham Tn/dng Thi Tho, Hoa hoc cdc hap chdt tu nhien, (1997).
[8] Biii Xuan Vffng, Mot sd phUcfng phdp phdn tich cdng cu trong hoa hQu co, (2009).
[9] Tran Van Sung, Cdc phuong phdp phdn tich vat l'^ trong hoa hoc, (2005).
[10] Pham Thi Bich Tuyet, Hap chdt tu nhien, (2006).
SUMMARY
FORMATION OF FAVORABLE COMPOUNDS FROM ORIENTED FERMENTATION OF WHOLE COFFEE TO PRODUCE COFFEE BEAN
Ta Chi Dong Luan, Le Thi Lien Thanh, Le Van Hoang The results in this study were obtained from series of previous investigations including the selection of basic nutrient medium, the determination on the ratio of coffee outer extract to the medium for the lactic bacterial isolation, stimulation and culture during the period of fermentation with coffee outer in order to get higher quality coffee at both aspects of flavour and colour. The outcome of the study is to exploit and apply the bacterial communities from the digestive tract of the skunk, the biological factors for the famous coffee "skunk coffee", aiming at increasing the value as well as the competition capacity of Vietnam coffee bean.
=Chi cue Tieu chuan Do lifcfng ChS't lifdng Binh Dinh, dnh Binh Binh ''Lien hiep cac Hgi Khoa hoc va Ky thuSt Da NSng
"Dai hoc Dong A
Ngay nhan bai: 02/4/2015; Ngay nhan dang: 17/4/2015