No abstract

Research interest on fiber has increased rapidly in the last decade due to its complexity and functional properties towards the human body. In this research group, pitaya (Hylocereus polyrhiuzus [F.A.C. Weber] Britton & Rose) stem flour is a promising candidate as new food resources since it contains a high amount of fiber and vitamin C as well as demonstrates both antioxidant and antibacterial activities. However, this pitaya stem flour has very low solubility in water that makes its application in food product very limited. In this study, pitaya stem flour has been fermented by Trichoderma reesei in a variation of inoculum concentration (3 % and 5 %) and fermentation time (24 to 60 h). The fermentation processes reduce the ash and water content of the flour, increase the soluble fiber content as well as its solubility. During the fermentation, the colour of the flour has changed. It becomes brighter and brownish. The best fermentation condition marked by its highest soluble fiber content is achieved by 3 % (w/v) of T. reesei inoculum with 60 h incubation time.

Abstract. Thermophilic bacteria producing chitinase were collected from Prataan hot spring, East Java, Indonesia and screened. The isolated bacterium was analyzed using 16S rRNA gene sequencing analysis and identified as Paenibacillus sp. The molecular identification was confirmed through morphological and physiological analyses. The production of chitinase was conducted at various incubation times, temperatures, pH and concentrations of colloidal chitin. The optimum condition of the isolate to produce the highest chitinase was 0.9% (w/v) of colloidal chitin (pH 7.0) at 48 °C for 24 hours. The obtained chitinases were optimally active at 55 °C and pH 6.0-7.0. The chitinases were gradually purified by ammonium sulfate precipitation, Sephadex G-100 gel filtration, followed by DEAE-cellulose ion exchange chromatography (IEC). The purification method gave a purification factor of 9.43 and a yield of 2.68%. Two protein fractions were obtained from sodium dodecyl sulfatepolyacrylamide gel electrophoresis (SDS-PAGE) with molecular weights of 68 and 82 kDa.

In this research we reported the synthesis of oligonucleotide-silver nanoparticle (OSN) conjugates and demonstrated their use along with magnetic beads as biosensor for Escherichia coli detection under magnetic field condition. Oligonucleotide DNA probes were conjugated on silver nanoparticles using alkanethiols linker. Two kinds of alkanethiols linker, 11-mercaptoundodecanoic acid (11-MUDA) and 16-mercaptophexadecanoic acid (16-MHDA) were compared to get the best probe conjugation yield and OSN UV-Vis absorption spectra properties. Three different methods of Escherichia coli DNA isolation i.e. Chen and Kuo (1993), Phenol Chloroform Isoamylalcohol (PCI) extraction and boiling lysis were also compared to explore the performance of the biosensor towards the DNA target purity. Detection process through hybridization between the DNA probe and the target was carried out at 55 o C for 1 hour incubation time. The results showed that 16-MHDA gave higher conjugation yield and higher OSN UV-Vis absorption spectra than 11-MUDA. The biosensor was able to detect the presence of the DNA target which was isolated from the three isolation methods. The best detection signal was achieved by Chen and Kuo isolation method in which it could detect the presence of the DNA target up to 1.3 ng/μL.