Bacterial cellulose (BC), produced by Acetobacter xylinum, has been given a great attention due to its high potency for many industrial applications. An optimized substrate is important for higher BC production; thus, an alternative natural product, as a carbon source, should be determined. This study aims at investigating the BC of A. xylinum cultured in coconut water and pineapple juice-based media and to predict its fermentation kinetics. The BC was produced on two stages of fermentation system, the shaking culture for propagation and the static culture fermentation for BC production. A. xylinum exhibited exponential phase at 48 h which showed BC production associated with its cell growth on both substrates. Fermentation kinetics of A. xylinum using coconut water and pineapple juice revealed Rp 0.117 and 0.051 g/l/h, Rx 0.309 and 0.133 g/l/h, Rs 0.079 and 0.215 g/l/h, Yx/s 1.408 and 0.240 g biomass/g glucose, Yp/s 3.612 and 0.599 g cellulose/g glucose, Yp/x 2.235 and 2.452 g cellulose/g biomass, µmax 0.0132 and 0.0082/h, σ 0.028 and 0.0173/h, respectively. Overall parameters of fermentation kinetics revealed a high rate of BC formation and efficient conversions of glucose to biomass and BC by A. xylinum on coconut water substrate. Thus, coconut water proved to be a more suitable substrate to produce BC in comparison with pineapple juice.

Partial Purification and Characterization of Chitinase from Entomopathogenic Fungus Beauveria bassiana Isolate BB200109. Yadi Suryadi, Tri P. Priyatno, I Made Samudra, Dwi N. Susilowati, Nuni Lawati, and Eman Kustaman. Beauveria bassiana is one of the entomopathogenic fungus that produces chitinase when infecting its host. This study was aimed to purify, isolate and characterize chitinase of B. bassiana isolate BB200109. Pathogen identity was determined both morphologically and molecularly using ITS primer, whilst characterization was done at various conditions i.e. temperature, pH, metal ion and incubation time. Results showed that the BB200109 isolate belonged to B. bassiana. The isolate produced extracellular chitinase with chitinolytic index of 1.035. Partial purification of three saturated ammonium sulphate precipitation (10, 30, and 70%) showed maximum purity of 1.2 times, while dialysis could increase the purity of 1.9 times compared to that of crude enzyme extract. Characterization results showed that the chitinase isolated from B. bassiana isolate BB200109 had an optimum activity at pH 4, temperature 50 o C, and optimum incubation time of 90 minutes. , and Na + acted as inhibitors. The chitinase demonstrated lower affinity to chitin substrate as indicated by high K m value of 0.266 mg/l and a V max of 0.067 mg/l sec. Based on SDS-PAGE, chitinase from B. bassiana isolate BB200109 had molecular weight of 60.25 kDa. The study implied the potency of B. bassiana isolate BB200109 as extracellular chitinase producer with its enzyme charateristics seems to be developed as an insect biocontrol agent.

Rice blast caused by Pyricularia oryzae is a major disease affecting rice production grown in upland and wetland rice. Application of beneficial bacteria as seedling root dip and spraying method to protect against the disease may be an alternative strategy to chemical control. This research was aimed to explore the bacterial consortium that may control blast disease on rice plants. In this study, the following bacterial cultures and their consortiums were used: Bacillus firmus E65, Serratia marcescens E31, Pseudomonas aeruginosa C32b, Bacillus cereus II.14, and its combination for their suppression ability against P. oryzae under in-vitro conditions. The results showed that A2 (Bacillus firmus E65) and A6 consortium (Bacillus firmus E65, Bacillus cereus II.14, and Pseudomonas aeruginosa C32b) significantly reduced the mycelial growth of P. oryzae with the percentage inhibition of 73-85% and 66-83%, respectively. Further greenhouse testing conducted with use of formulative preparation of the two selected best treatments using talc, bentonite, palm oil, and suspensionbased carriers showed that spraying with suspension formulation had good effect in suppressing blast disease compared with that of other carriers evaluated.

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<p>Anthracnose (Colletotrichum gloeosporioides) is one of the important diseases of fruit crops that need to be controlled. This study was aimed to obtain the best formula of hydrolyzed nano chitosan and its potensial in controlling anthracnose. The hydrolyzed chitosan was prepared using chitinase enzyme extracted from Burkholderia cepacia isolate E76. Chitosan nanoparticles were synthesized using ionic gelation method by reacting hydrolyzed chitosan (0.2%) with Sodium tripolyphosphate (STPP) (0.1%) as cross-linking agent using 30&amp;ndash;60 minutes stirring condition. The bioactivity of the nano chitosan formula was tested to C. gloeosporioides under in vitro and in vivo assays. The specific enzymatic activity of the purified chitinase was higher (0.19 U/mg) than that of crude enzyme (supernatant) with the purity increased by 3.8 times. Of the four formula tested, Formula A (hydrolyzed chitosan to STPP volume ratio of 5 : 1 with 60 minutes stirring condition) was found good in terms of physical characteristic of the particle. The formula nano chitosan particle had the spherical-like shape with an average particle size of 126.2+3.8 nm, polydispersity index (PI) of 0.4+0.02, and zeta potential (ZP) value of 27.8+0.2 mV. Nano chitosan had an inhibitory activity to C. gloeosporioides in vitro up to 85.7%. Moreover, it could inhibit 61.2% of C. gloeosporioides spores germination. It was shown that nano chitosan was also effective to reduce anthracnose disease severity in vivo when applied as a preventive measure on chili and papaya fruits. This study could be used as a reference for further fruit coating application using nano chitosan as a promising postharvest biocontrol agent to C. gloeosporioides.</p>

Penyakit blas (Pyricularia oryzae) di Indonesia awalnya hanya merusak tanaman padi gogo, namun penyakit blas dilaporkan terjadi pada tanaman padi sawah sejak tahun 2000-an. Aplikasi cendawan endofit merupakan salah satu cara pengendalian yang berpotensi besar untuk dikembangkan. Penelitian ini bertujuan untuk mendapatkan cendawan endofit dari padi sawah yang berpotensi menekan keparahan penyakit blas. Isolasi cendawan endofit dilakukan dari bagian akar, batang, dan daun tanaman padi sawah. Varietas Kencana Bali digunakan pada pengujian penghambatan P. oryzae secara in vivo karena varietas tersebut merupakan varietas paling rentan terhadap penyakit blas. Sebanyak 47 isolat cendawan endofit berhasil diisolasi dari tanaman padi sawah asal Bogor, Sukabumi, dan Blitar. Berdasarkan morfologi koloni cendawan endofit dapat dibedakan menjadi 9 morfotipe. Sebanyak 4 dari 14 cendawan endofit menunjukkan aktivitas antibiosis pada pengujian penghambatan P. oryzae secara in vitro. Hasil pengujian penghambatan penyakit blas pada varietas Kencana Bali di rumah kaca menunjukkan bahwa 4 isolat tersebut mampu menekan perkembangan penyakit blas dengan tingkat penekanan antara 30-70%.