Optimization of Bioethanol Synthesis from Durian Seeds Using Saccharomyces Cerevisiae in Fermentation Process

Bioethanol is an alternative energy of environmentally friendly as a substitute for petroleum. Sucrose, starch, and fibrous cellulose (lignocellulose) are the main ingredients for bioethanol production. The material is very easy and abundant to get from the waste of agricultural crops. One of these agricultural wastes in Indonesia that have not been used optimally is durian seeds. Durian seeds only become waste and are not commercially useful, even though they contain high carbohydrates, which is possible as a potential new source for bioethanol production. In this work, an experimental study was conducted on bioethanol synthesis from durian seeds through fermentation by Saccharomyces cerevisiae yeast in aerobic fermenter. The process for the production of starch-based bioethanol includes milling, hydrolysis, detoxification, fermentation, and distillation. At the stage of fermentation, variations in the duration of fermentation were applied for 1-11 days. Carbohydrates contained in durian seed flour are 11.541%, which is the largest content. The highest result of ethanol content is 14.72 % (v/v) in 9 day fermentation periods by using Saccharomyces cerevisiae in aerobic conditions. Distillation to enrich bioethanol was carried out by batch vacuum distillation at 68°C for ± 180 minutes and produced bioethanol with a purity of 95%.

The Mosquito Repellent Activity of the Active Component of Air Freshener Gel from Java Citronella Oil (Cymbopogon winterianus)

This study examines the active component of Cymbopogon winterianus (Java citronella) oil, as a green mosquito repellent, obtained through a steam distillation method. Java citronella oil, which contains citronellol, citronellal, and geraniol, was isolated by batch vacuum fractional distillation, and their effect was tested against the dengue fever (DF) vector, known as Aedes aegypti. Furthermore, air freshener gels were formulated with Java citronella oil, carrageenan, gum, sodium benzoate, ethylene glycol, polysorbate 20, sodium chloride, and distilled water, at varying concentrations. The results show that formula I has the best controlled release evaporation for citronellal, citronellol, and geraniol, as well as the best storage time of 16.82 days and 12.77 days for geraniol and citronellol, respectively. The most significant specific gravity (0.0136) was recorded in formula V, while gel formula I exhibited the highest level of instability at 35°C, with a syneresis value of 77.11% in t=72 h and pH 5.33. In addition, formula IV at 5°C demonstrated the highest syneresis (75.34%) in t=72 h, with pH 7.04, while a peak viscosity of 100,958 cP was recorded in formula IV. The repellent activity of each active component was measured based on the period of protection conferred against the bites of Aedes aegypti within one hour, and the results showed geraniol and citronellol, with respective activity of 78.00%±4.83 and 77.34%±3.57, as the most effective.

Maintaining Low Voiding Solder Die Attach for Power Die While Minimizing Die Tilt

This paper addresses work to minimize voiding and die tilt in solder attachment of a large power die, measuring 9.0 mm × 6.5 mm × 0.1 mm (0.354″ × 0.256″ × 0.004″), to a heat spreader. As demands for larger high power die continue, minimizing voiding and die tilt is of interest for improved die functionality, yield, manufacturability, and reliability. High-power die generate considerable heat, which is important to dissipate effectively through control of voiding under high thermal load areas of the die while maintaining a consistent bondline (minimizing die tilt). Voiding was measured using acoustic imaging and die tilt was measured using two different optical measurement systems. 80Au-20Sn solder reflow was achieved using a batch vacuum solder system with optimized fixturing. Minimizing die tilt proved to be the more difficult of the two product requirements to meet. Process development variables included tooling, weight and solder preform thickness.