Judul: Beberapa Khamir Tape Pada Fementasi Singkong Pahit
Abstrak: Diisolasi beberapa koloni yang diduga koloni khamir dari dua macam ragi tape yang berasal dari perusahaan ragi "Roda Mas" Surakarta. Keduanya dibedakan menurut cap dan warna capnya yakni cap Roda ABC berwarna merah dan cap Roda R berwarna biru. Kemudian diamati pengaruh isolat-isolat yang memiliki aktifitas amilase pada fermentasi singkong pahit SPP (Sao Pedro Petro). Pengamatan dilakukan terhadap aktifitas amilase isolat-isolat ragi tape, kadar HCN, kadar air serta aroma, tekstur, dan penampakan dari tape singkong SPP. Hasil pengamatan menunjukkan bahwa ada 20 isolat khamir ragi "Roda Mas Surakarta dan ragi-ragi lainnya yang memiliki aktifitas amilase. Fermentasi singkong SPP dengan inokulum biakan murni khamir ragi "Roda Mas" Surakarta meningkatkan kadar HCN bebas dari bahan walaupun bahan sebelumnya sudah direndam dalam air mengalir selama 24 jam dan disterilkan dalam otoklaf dan mengalami penurunan kadar HCN bebas yang cukup besar, yakni dari 154,34 mg/kg bobot kering menjadi 44,64 mg/kg bobot kering. Kadar air agak meningkat.
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Judul: Isolasi dan Penapisan Khamir Penghasil Asam Sitrat dari Tape dan Konsorsium Ragi Tape
Abstrak: Fermentasi tape menghasilkan rasa manis yang khas, beralkohol, dan sedikit rasa asam yang mungkin dihasilkan oleh ragi tape yang merupakan konsorsium mikroorganisme, termasuk khamir. Penelitian ini bertujuan untuk mendapatkan isolat khamir yang mampu menghasilkan asam sitrat dari empat sampel tape dan dua sampel ragi tape menggunakan metode spread plate pada media Prescott agar. Koloni diamati dengan mikroskop stereo dan mikroskop cahaya. Isolat khamir dipilih berdasarkan nilai satuan asam, diikuti oleh analisis total asam kuantitatif menggunakan titrasi asam. Sebanyak 30 isolat yang mampu menghasilkan asam organik yang mungkin termasuk asam sitrat berhasil diisolasi. Isolat-isolat ini terdiri dari beberapa genus termasuk Saccharomyces sp., Candida sp., Pichia sp., Wickerhamomyces sp. Spesies khamir yang diduga menghasilkan asam sitrat berasal dari genus Saccharomyces, yaitu isolat KhR1.4 yang menunjukkan produksi asam tertinggi sebanyak 3,1 g/L setelah 84 jam kultivasi cair. Penurunan parameter pH menunjukkan adanya asam yang dihasilkan oleh khamir. Oleh karena itu, khamir yang diisolasi dari tape dan konsorsium ragi tape berpotensi untuk dieksplorasi lebih lanjut dalam produksi asam sitrat., Fermentation of tape produces a distinctive sweet, alcoholic, and a hint of sour taste that could be generated by a consortium of microorganisms, including yeasts. We conducted yeast isolation that could produce citric acid from four samples of tape and two samples of tape starters using the spread plate method on Prescott agar. Colonies were observed under a stereo microscope and light microscope. Yeast isolates were then selected based on their Acid Unit values, followed by quantitative total acid analysis employing acid titration. A total of 30 isolates capable of producing organic acids which might include citric acid were obtained. These isolates consisted of several genera including Saccharomyces sp., Candida sp., Pichia sp., Wickerhamomyces sp. Yeast species suspected to produce citric acid belong to the genus Saccharomyces, i.e. isolate KhR1.4 which showed the highest acid production as much as 3.1 g/L of acid after 84 hours of liquid cultivation. The decreased in pH parameter indicating the presence of acid produced by the yeast. Therefore, yeasts isolated from tape or tape starters have the potential to be explored further for citric acid production.
Keyword: citric acid, fermentation, colonies, Prescott, titration

Judul: The Construction of Greedy SVP LLL Algorithm
Abstrak: A lattice is a set of all integer linear combination of a set of linearly independent vectors in ℝ𝑛���. The independent vectors are called bases of lattice. Any lattice can be generated from many bases, and these bases have the same cardinality. In the lattice, the most fundamental and renowned problem is the Shortest Vector Problem (SVP). SVP is a tracking problem of the shortest nonzero vector in a lattice with equivalent bases. In two dimensions, SVP problem has resolved exactly by Gauss’ algorithm. When the lattice dimension is higher than two, A.K. Lenstra, H.W. Lenstra and L. Lovasz gave a LLL algorithm to compute approximation of nonzero shortest vector in the lattice. Reduced bases solution obtained from LLL algorithm still be an approximation and has polynomial running time of arbitrary dimension which large enough. In 1994, Schnoor and Euchner modified this LLL algorithm as a new variant which later was named deep insertion LLL algorithm. This algorithm is a modified version of the LLL algorithm to the terms of the exchange step to improve the accuracy of output of LLL reduced bases and applying it to the subset sum problem. The purpose of this research are: (1) Reconstruct the LLL algorithm and deep insertion LLL algorithm using a geometric approach. (2) Construct a greedy SVP LLL algorithm. (3) Implement the three algorithms in a symbolic programming language, and evaluate them experimentally. A bases ℬ=[𝐛���1,𝐛���2,…,𝐛���𝑛���] in ℝ𝑚��� is called reduced LLL with parameter 𝛿��� if satisfies: (a) |𝜇���𝑗���𝑖���|≤12, for every integer 𝑖���,𝑗��� with 1≤𝑖���<𝑗���<𝑛���. (b)𝛿���‖𝜋���𝑗���(𝐛���𝑗���)‖2≤‖𝜋���𝑗���(𝐛���𝑗���+1)‖2, for 𝑗���=1,2,…,𝑛���−1,where 𝛿��� is a reduced parameter of real numbers with 14<𝛿���<1. The first requirement is the reduced basis 𝛿��� must “nearly orthogonal” and in its computation case, this requirement can be reached out by using the Gram-Schmidt’s orthogonalization. While the second requirement is called exchange step, or used to called as Lovasz condition. By using both of these requirements, then they establish the LLL algorithm. Then, Schnoor and Euchner modify the LLL algorithm based on the requirements of the exchange step called the deep insertion LLL algorithm, where the exchange step is based on the comparison of the projected vector in orthogonal complement [𝐛���1,𝐛���2,…,𝐛���𝑘���−1]⊥ after j-th reduction. To construct greedy SVP LLL algorithm, the requirements of the exchange step is based on purely by comparing norm of lattice 𝐛���𝑗��� with norm lattice 𝐛���𝑖��� for 𝑖���=1,2,3…,𝑗���−1. The process of insertion reduced vector after the exchange step also has done greedily. Then, we calculate the number of arithmetic operation in greedy SVP LLL algorithm for further analysis. The result of our exprimentation for three algorithms on the certain matrix size shows that the running time of the three algorithms increases propotional to the size of the matrix. The result also shows that by using 𝛿���=34 for the LLL algorithm and the deep insertion LLL algorithm, and the greedy SVP LLL algorithm which is a new variant made by using no parameter of 𝛿���, outperform of the other of two previous algorithm in terms of speed with the same output.
Keyword: LLL algorithm, LLL deep insertion algorithm, greedy SVP LLL algorithm