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Abstrak :
Microbial communities usually have mixed populations, only in unique environmental situations do microorganisms live entirely alone. Thus many types of interactions are possible among the members of an ecosystem?s community. In general, the constant association of different organisms in an ecosystem is referred to as symbiosis, with the associates being called symbionts. One type of a symbiosis is antagonism. Antagonism is a symbiotic relationship in which one population of microorganisms has a harmful effect on the growth of another microbial population (Batzing 2002: 696). A number of microorganisms (bacteria, yeasts, fungi) which effectively control postharvest pathogens have been identified as antagonists (Mari and Guizzardi 1998:60). A variety of microbial antagonists were reported to control several different pathogens on various fruits. The organism that suppresses the pest or pathogen is referred to as the biological control agent (BCA) (Pal & Mcspadden Gardener 2006: 1). Biological control may in simple terms be defined as the use of one living organism to control another (Druvefors 2004: 4). Often antagonists are isolated on the surface of plants; this natural presence makes them more likely to succeed because of their colonization ability and environmental adaptation (Mari and Guizzardi 1998:60). The use of yeasts as antagonists appears to be quite promising, although the mechanism has not yet been fully elucidated. Some antagonist yeasts have been reported as biocontrol agent of fungal pathogen on fruits. Zhao et al. (2008: 115--116) reported that tomato fruit treated with Pichia guillermondii had an infection rate of 25% which was caused by Rhizopus nigricans, which was significantly lower than the control (41.67%). Kalogiannis et al. (2006: 72) reported that Rhodotorula glutinis Y-44 significantly reduced disease incidence caused by Botrytis cinerea on tomato by 52%, compared to the untreated control. Zhang et al. (2004: 84) reported that the application of Cryptococcus laurentii resulted in low average decay incidence caused by B. cinerea in fruit by 7.1%, compared with 40% in the water-treated control fruit. University of Indonesia Culture Collection (UICC) collected epiphytic yeasts from plant samples of Cibodas Botanical Garden, and moulds from decayed tomatoes and infected plants. The ability of the epiphytic yeasts as biocontrol agents against tomato spoilage-causing moulds has not been reported. This study consists of two parts. Part 1 is The Antagonistic Ability of Epiphytic Yeasts of Cibodas Botanical Garden on Tomato Plant Infected-Causing Moulds. Part 2 is The Potential of Candida sp. UICC Y-328 as a Biocontrol Agent of Aspergillus ochraceus on Postharvest Tomatoes.The purposes of this study were to investigate the ability of six species of epiphytic yeasts in inhibiting the growth of tomato plant infected-causing moulds, and the potential of Candida sp. UICC Y-328 as a biocontrol agent in reducing postharvest tomato spoilage caused by Asp. ochraceus. The media used for growing the yeasts was Yeast Malt Agar (YMA), and maintenance for fungi was Potato Dextose Agar (PDA). The media used for antagonistic test were PDA and Potato Dextrose Broth (PDB). Antagonistic test by strip method was carried out by using the concentrations of yeast cells at (0.7--4.45) x 108 CFU/ml, and Asp. ochraceus at (7.0--8.1) x 107 CFU/ml, Asp. terreus Thom at (7.7--8.6) x 107 CFU/ml and Drechslera sp. at (0.45--3.5) x 105 CFU/ml. The yeast cells were inoculated 4 hours earlier before inoculation of mould spores on PDA in Petri dishes. Results showed that Candida sp. UICC Y-328 has highest percentage of colony reduction of Asp. ochraceus (56.45%), followed by Metschnikowia reukaufii UICC Y-351 on reducing colonies of Asp. terreus and Drechslera sp. (25.42% and 51.28%, respectively) during 6-day incubation. Antagonistic test by co-culture method was carried out by using the concentrations of yeast cells at (0.7--4.45) x 108 CFU/ml, and Asp. ochraceus at (6.0--8.6) x 107 CFU/ml, Asp. terreus at (4.6--9.5) x 107 CFU/ml. The yeast cells were inoculated 8 hours earlier before inoculation of mould spores on PDB. Results showed that Candida sp. UICC Y-328 reduced the size of conidial heads (5.52%) and hyphae (8.29%) of Asp. ochraceus, at 3-day incubation. Cryptococcus laurentii UICC Y-379 reduced the size of conidial heads and hyphae of Asp. ochraceus (15.07% and 11.60% respectively) and Asp.terreus (12.35% and 24.47% respectively) at 3-day incubation. Antagonistic test by slide culture method showed that the yeast cells of four strains (Candida rancensis UICC Y-326, Cr. laurentii UICC Y-319, Cr. laurentii UICC Y-379,and M. reukaufii UICC Y-351) attached to hyphae of Drechslera sp. after 3- and 4-day incubation. Cells of Candida sp. UICC Y-328 attached to hyphae of Drechslera sp. after 4-day incubation. Cells of Cr. laurentii UICC Y-385 was not able to attach to hyphae of Drechslera sp. Candida sp. UICC Y-328 was potential in reducing the growth of Asp. ochraceus, and was investigated further for its potential as a biocontrol agent. Wounds on postharvest tomatoes were inoculated with 25 µl of yeast cell suspension and 25 µl of mould spore suspension. The yeast cells were inoculated 24 hours earlier before inoculation of mould spores on wounds of tomatoes. Biocontrol study showed that incidence of spoilage in postharvest tomatoes which were wounded and inoculated with Candida sp. UICC Y-328 and Asp. ochraceus, were reduced by 20% after 15-day incubation at room temperature. All postharvest tomatoes which were wounded and inoculated with Asp. ochraceus as control, were spoiled (100%). Synthetic fungicide Dithane M-45 at a concentration of 0.08% reduced spoilage incidence by 70%. Candida sp. UICC Y-328 was not effective as biofungicide in reducing spoilage incidence.

Abstrak :
Potensi Usaha Mikro Kecil Menengah kota Depok sangat beragam dan berkembang pesat dikarenakan posisi kota yang strategis, diapit oleh Kota Jakarta dan Kota Bogor. Namun, khusus pada jajanan kuliner belum dijamin keamanannya dari adanya cemaran mikroba patogen dalam makanan dan minuman. Adanya cemaran mikroba patogen pada makanan dan minuman dapat menimbulkan resiko penyakit. Penelitian ini dilakukan untuk mengidentifikasi ada atau tidaknya cemaran mikroba patogen pada sampel susu kedelai usaha rumahan. Sampel pengujian ini diambil dari tujuh produsen susu kedelai usaha rumahan yang menjajakan dagangannya di sekitar kampus Universitas Indonesia.Uji yang dilakukan meliputi penetapan Angka Lempeng Total (ALT), Angka Kapang Khamir (AKK), Angka Paling Mungkin (APM) Coliform, serta identifikasi Escherichia coli, Salmonella-Shigella, Staphylococcus aureus, dan Pseudomonas aeruginosa yang mengacu pada metode dalam SNI 7388-2009.Dari tujuh sampel susu kedelai yang diperiksa menunjukkan sampel A, B, C, dan D tercemar sedangkan sampel E, F, dan G tidak tercemar mikroba patogen. Hasil tersebut menunjukkan bahwa belum seluruh sampel susu kedelai terjamin kualitasnya secara mikrobiologis.

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Potential of Micro, Small and Medium Enterprises Depok city is very diverse and is growing rapidly due to the strategic position of the city, flanked by Jakarta and Bogor. However, especially in the culinary snacks yet secured from the presence of pathogenic microbial contamination in foods and beverages. The presence of pathogenic microbial contamination in foods and beverages can cause the risk of disease. This research conducted to identify the presence or absence of pathogenic microbial contamination in soy milk sample home-based business. The test samples were taken from seven manufacturers of soy milk home-based businesses that peddle his wares around the campus of the University of Indonesia. Testing was conducted on the determination of Total Plate Count(TPC),mold-yeast count (AKK), most probable number (MPN), as well as the identification Escherichia coli, Salmonella - Shigella, Staphylococcus aureus, and Pseudomonas aeruginosa which refers to the method in SNI 7388 - 2009.From seven samples of soy milk were examined showed a sample A, B, C, and D contaminated while samples E, F, and G are not pathogenic microbes uncontaminated. These results indicate that not all soy milk samples microbiological quality assured.

Abstrak :

Masalah lingkungan seperti polusi sistem perairan telah mendorong urgensi penyusunan teknologi pengolahan limbah yang lebih baik. Nitrat adalah salah satu target pencemar yang digunakan dalam asesmen kualitas air. Saat ini, proses biologis untuk eliminasi nitrat dari sistem perairan sedang dikembangkan sebagai alternatif untuk proses-proses fisika-kimia yang sering digunakan. Microbial electrolysis cell (MEC) adalah teknologi baru yang diajukan untuk tujuan tersebut. Penelitian ini bertujuan memasangkan proses eliminasi nitrat dengan produksi biohidrogen (bio-H₂) di sistem MEC. Cakupan studi ini adalah dua sistem yang disebut mini-MEC dan MEC. Kedua sistem tersebut dibedakan berdasarkan volumenya. Parameter optimum operasi (V_ext dan sumber karbon) ditetapkan pada sistem mini-MEC sebelum beralih ke sistem MEC. Kondisi optimum ditentukan pada V_ext 0,7 V dengan asetat sebagai sumber karbon terbaik. Sistem dievaluasi berdasarkan performa luaran elektrikal (I_d, P_d), eliminasi nitrat (RE%, R_NO3-), dan produksi bio-H₂ (H_max, R_H2, dan Y_H2). Konsorsium desain (kode konsorsium: IS dan IW) disusun berdasarkan hasil penelitian sebelumnya dengan kinerja eliminasi nitrat dan lokasi isolasi sebagai kriteria desain. Konsorsium desain dibandingkan dengan konsorsium alam (S) di MEC skala 100 mL untuk proses simultan eliminasi nitrat dan produksi biohidrogen. Konsorsium IS memberikan hasil terbaik dari segi profil produksi biohidrogen dengan H_max 10,6515 mg L^-1, Y_H2 6,491 mg g^-1, dan R_max 0,0867 mg L^-1 jam^-1. Konsorsium alam S memberikan performa terendah dari ketiga konsorsium yang diuji. Data dari konsorsium IS dievaluasi terhadap model untuk pertumbuhan dan produksi biohidrogen. Model Gompertz dan logistik termodifikasi dapat mendeskripsikan data dengan baik berdasarkan parameter fit R². Estimasi parameter model dilakukan melalui metode non-linear least square. Hasil estimasi parameter model Gompertz yang telah dioptimasi adalah 0,1659 untuk R_max, 10,2495 untuk H_max, dan 30,0607 untuk l. Selanjutnya, studi ini dapat dikembangkan ke arah penyusunan model prediktif profil bio-H₂ pada sistem MEC berdasarkan hubungan linear antara profil bio-H₂ dan pertumbuhan sel.

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......Environmental problems, especially pollution to water systems have urged research into cleaner wastewater treatment strategies. Nitrate is one of the main targets for water quality control. The use of biological processes to remove nitrate from water systems is being studied as alternatives to current physico-chemical practices. Microbial electrolysis cell (MEC) emerged as a new technology that is appropriate for this purpose. This research aim to pair nitrate elimination with biohydrogen production in MEC. The study worked on two scales of MECs, referred to as mini-MEC (20 mL) and MEC (100 mL). Operating parameters (V_ext and carbon source) was determined on mini-MEC using axenic cultures of known denitrifying bacteria. V_ext was set at 0.70 V and CH₃COONa was selected as carbon source for subsequent experiments. System was evaluated based on electrical outputs (I_d, P_d), nitrate elimination (RE%, R_NO3-), and biohydrogen production (H_max, R_H2, and yield). Synthetic microbial consortia were designed based on isolates obtained in a previous research using nitrate elimination and site characteristics as design criteria. Designed consortia (IS and IW) was compared against naturally occurring soil microbial consortium (S) in 100 mL MEC for simultaneous biohydrogen production and nitrate elimination. Consortium IS yield better biohydrogen production profile with H_max of 10.6515 mg L^-1, Y_H2 at 6.491 mg g^-1, and R_max 0.0867 mg L^-1 h^-1. Consortium S performed the worst out of three with declining H₂ concentration curves at later operation period. The data from consortium IS was evaluated against models for bio-H₂ production. Modified Gompertz model could describe the data well based on comparison of fit parameter R² against modified logistic model. Model optimization was carried out by non-linear least square methodology. Optimized parameter values were 0.1659 for R_max, 10.2495 for H_max, and 30.0607 for l. Future studies should explore the design of a predictive model for H₂ production based on microbial growth in MEC inoculated with microbes with similar profile to IS consortium.