Saputro TB, Prayogo Y, Rohman FL, Alami NH. 2019. The virulence improvement of Beauveria bassiana in infecting Cylas formicarius modulated by various chitin based compounds. Biodiversitas 20: 2486-2493. Sweet potato (Ipomoea batatas L.) is one of alternative carbohydrate source with an important role in food production, animal feed industries, and as raw materials for other derivatives. However, severe losses are constantly occured in its production due to a notorious pest known as sweet potato weevil (Cylas formicarius). The chemical insecticides commonly used to treat the pest, but have not been efficient in eliminating C.formicarius. Beauveria bassiana is well known as a biological control agent, has been identified to effectively eliminate the pest. The aim of this research is to observe the optimum concentration of several chitin-based compounds in improving the virulence of B. bassiana. The research was conducted by the addition of chitin from various sources -insects, crustaceans and mollusk shells in a growth medium of B. Bassiana. Moreover, conidia produced by B.bassiana was exposed to C.formicarius to investigate the mortality rate of this insect. The results showed four different characteristics of colonies -velvety, wooly, pellicular, and farinaceous. The 1% chitin from Tellina sp, (P9), was found to be the best treatment which increased the growth of the colony diameter attaining 6.7cm in 20 days, increased the conidia viability that reaches 93.5%. In addition, the highest mortality percentage of C. formicarius was 91.67% in P9 at 6 days after infection. Overall, this research gave new potential sources of chitin that can be applied in improving the virulence of B. Bassiana in eliminating C. formicarius.
Abstract.Lipase is an enzyme that is often used in industry and become a commercial enzyme. One group of microorganisms capable of producing lipase is a yeast. This study aims to screen yeast from Wonorejo mangrove that potential to produce lipase and to optimize the production of these enzymes. Screening test include the measurement of lipolytic index and value of fatty acid. Yeast with the best value of fatty acid will be continued to the measurement of lipase activity. It is affected by several environmental factors, such as pH, temperature, and incubation time. This research was conducted to observe the optimization variation on environmental factors combination to produce lipase. Lipase activity was tested by using p-Nitrophenyl Palmitate (pNPP). Absorbency was measured by spectrofotometer on wavelength of 410 nm. Measurement of the enzyme activity was done by interpolating the absorbance values on the p-nitrophenol standard curve then calculated by the formula. All data were analyzed by using descriptive quantitative method. The results show that the highest lypolityc index was 2.08. The highest value of fatty acid was 0.49 that was reached on 168 hours of incubation. Candida W3.8 expressed the highest lypolylitic potential. The optimum environment to produce lipase by Candida W 3.8 was on 120 hours of incubation time, in temperature range of 27 C -45 C and pH range of 4,5 -7.
This paper presents the experimental study on the penetration of chloride ions in fly ash based-geopolymer concrete in the salt-water. To determine the corrosion possibility of reinforcement, lollipop-shape specimens with the size of 10x10x15 cm were prepared with the plain steel bar in the middle of concrete. The specimens were exposed to chloride ion penetration for 30-120 days. The mixtures were varied with alkali concentration of 8M-12M with the mass ratio of Na2SiO3 to NaOH was varied from 1.5 to 2.5. Specimens made with portland cement concrete was also prepared as the control. The best performance was showed by specimens made with 12M of NaOH. Due to ion exchange on the surface of geopolymer concrete, less chloride ion was found in geopolymer made with high alkali concentration. After 90 days, Portland cement concrete showed less performance while geopolymer concrete showed the strength increasing. High binding capacity due to soluble silicate content in geopolymer concrete was one of the reasons why geopolymer specimens are more resistant to chloride ion penetration.
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