Judul: Potensi Enzim -Galaktosidase dari Lactobacillus plantarum Strain B123 Indigenous untuk Hidrolisis Laktosa pada Susu UHT
Abstrak: Lactose concentration in milk is 4.6% (w/w) in average (Walstra 2006). The content of lactose with less than 1% (w/w) of final product is acceptable for people with lactose intolerance problem (Tuure and Corpela 2004). Enzymatic hydrolysis of lactose is one of the important biotechnological processes in the milk industry because of some beneficial effects including the elimination of lactose in milk for people with lactose intolerance, prevention of lactose crystallization and contribution to the product sweetness (Jurado et al, 2002). -Galactosidase enzyme can be produced by lactic acid bacteria. In this study, indigenous Lactobacillus plantarum strain B123 was isolated from Indonesian traditional fermented vegetable product. The use of this local potential strain was to increase its role to the added value products such as low lactose UHT milk. Even though low lactose UHT milk product has not been commercially marketed yet in Indonesia, however the need of low lactose milk for people with lactose intolerance was already present. This research was aimed to: (1) determine the growth condition of indigenous Lb. plantarum strain B123 to produce β-galactosidase (2) determine the production condition of -galactosidase from Lb. plantarum B123 strain with partial purification and (3) determine the potential of β-galactosidase from indigenous Lb. plantarum B123 strain to hydrolyze lactose of full cream and low fat-UHT milks, containing total fat 3.5 and 1.0% (w/v) respectively, in batch process. The result showed that the growth condition of indigenous Lb. plantarum B123 in MRSB to produce β-galactosidase were 2% inoculum, 1% of lactose, medium pH 8, and 24 h incubation time at 37°C. The enzyme showed an optimum activity to hydrolyzed oNPG substrate at pH 6.5 and temperature 50°C . Specific activity of -galactosidase has increased during the partial purification given 15.05 U/mg in crude enzyme to 109.58 U/mg in dialysed enzyme (at first production) and 87.09 U/mg in crude enzyme to 109.58 U/mg in dialysed enzyme (at second production). Lactose in full cream-UHT milk was hydrolyzed at a maximum rate of 60.0% (lactose concentration from 3.82% w/v to 1.52% w/v) and in low fat-UHT milk 81.1% (lactose concentration from 4.44% w/v to 0.84% w/v) by 7.2 U β-galactosidase/mL milk for 9 h at 50°C. Enzyme concentration, hydrolysis time and total fat concentration had a significant influence on the hydrolysis of lactose in UHT milk (p<0.05). According to the different analytical methods to monitor the lactose hydrolysis, a correlation between the results of glucose concentrations in full cream-UHT milk analyzed by GOD-POD kit and HPLC was observed. There was a positive correlation between analysis of glucose concentrations in full cream-UHT milk with GOD-POD kit and HPLC (r = 0.923).
Keyword: 

Judul: Amobilisasi β-galaktosidase Bakteri Asam Laktat Indigenos Strain D-210 dengan Natrium Alginat dan Potensi Hidrolisisnya pada Susu UHT
Abstrak: Lactose intolerance is a symptom who cannot produce the β-galactosidase enzyme (lactase) an enzyme that catalyzes hydrolysis of lactose into glucose and galactose, in their digestive system. In most cases this causes symptoms which may include abdominal bloating and cramps, flatulence, diarrhea and nausea. Immobilization of Indigenous Lactic Acid Bacteria strain D-210 β-galactosidase with natrium alginate and its potential in UHT milk has not been reported yet. Indigenous Lactic Acid Bacteria strain D-210 was found as bacteria producing β-galactosidase which was culture in MRS (Mann Rogosa Sharpe) and substrate lactose 3%. The β-galactosidase was dialyzed for getting the partial pure. The research results showed that the optimum production of β-galactosidase in Indigenous Lactic Acid Bacteria Strain D-210 was reached on 24 hours with activity 26.605 U/ml and total activities was 27.669 U, and Indigenous Lactic Acid Bacteria Strain D-210 optimum growth was reached on 24 hours with optimum optical density 1.984 and amount of cell was 1.81x10-8 cell/ml. The total activities partial purification of crude β-galaktosidase was 138.396 U, total activities after presipitation with amonium sulfat the total activities was 87.030 U and total activities after dialysis was 50.420 U. The inhibitors of β-galaktosidase were Hg and Cu with relative activities were 56.82% and 1.04%, while the activators were Mg,Mn,Ca,Co,Zn. Kinetic parameter of enzyme showed that the values of Km: 0.491 mM and Vmax:0.093 μmol/minute (free β-galactosidase), and values of Km:15.54 mM and Vmax 0.474 μmol/minute (immobilized β-galactosidase) . The optimum activity of the free β-galactosidase was reached on pH: 6.5 with activity 252.341 U/ml, and temperature: 45 oC with activity 180.093 U/ml. The optimum concentration of Na alginate for immobilized cell and β-galactosidase were 2% and 3% respectively. The concentration of Na alginat used for hydrolysis lactose in cell was 12% with the released total product 58.884 μmol and for the β-galactosidase was 20% with the released total product 91.752 μmol. The optimum activity of the immobilized β-galactosidase was reached on pH:6 with activity 40.428 U/ml, and on temperature: 40 oC with activity 41.194 U/ml. The optimum potential of cell imobilized and β-galactosidase for lactose hidrolysis in UHT milk were reached for 6 hours and 18 hours with relative activity 76.72% and 62.78% respectively. Repeated use of cell and enzyme β-galactosidase immobilized was 6 times with the use of relative hydrolisis activity were 39.52% and 53.68% respectively.
Keyword: 

Judul: Closed Knight’s Tour pada Papan Catur Berbentuk Persegi Panjang dengan Ukuran Maksimal 8 × 8
Abstrak: Closed Knight’s Tour merupakan langkah kuda yang mengunjungi setiap kotak pada papan catur tepat satu kali dengan langkah kuda berawal dan berakhir pada kotak yang sama. Graf yang terbentuk dari closed knight’s tour dinotasikan sebagai graf G(m,n), dengan m adalah banyaknya baris dan n adalah banyaknya kolom. Graf tersebut memuat Hamiltonian cycle. Sebuah graf terhubung G adalah graf bipartite jika dan hanya jika graf tersebut tidak memiliki cycle dengan panjang ganjil. Papan catur yang memenuhi syarat cukup untuk memiliki closed knight’s tour adalah papan catur berukuran 5 × 6, 5 × 8, 6 × 6, 6 × 7, 6 × 8, 7 × 8, dan 8 × 8.
Keyword: bipartite, closed knight’s tour, hamiltonian cycle, knight’s tour, teori graf