Iranian Journal of Chemical Engineering (IJChE)

Abstract In this essay, lipase from Burkholderia cepacia was immobilized into 3-glycidoxypropyltrimethoxysilane (GPTMS) and tetramethoxysilane (TMOS) derived sol-gels. GPTMS:TMOS molar ratio of 1:3 was found to yield the best result. The morphological characteristics were investigated based on SEM and BET analysis. Sample mean pore diameter was 39.1 nm, it had a specific surface area of 60 m2/g prior to enzyme addition which decreased to 7.49 m2/g after immobilization. The enzyme activity was assessed through transesterification of waste cooking oil in the presence of ethanol with optimal conditions of: 40 ᵒC, 15 % immobilized lipase, 9:1 alcohol to oil molar ratio in 24 h of reaction which resulted to 91.70 % biodiesel production. In six-hour reaction time, 86.87 % biodiesel was obtained which is much shorter than conventional enzymatic transesterification which is 72 hours. Ethyl esters were characterized by determining their viscosity, density, and flash point based on ASTM D 6751-07b standards.

Abstract In this research, unstructured kinetic modeling for cell growth evaluation by X.campestris, xanthan production and sugar cane molasses consumption in a batch culture were investigated. Logistic model for biomass growth, Luedeking-Piret model for xanthan biopolymer production and modified Luedeking-Piret model for sugar cane molasses consumption provides an accurate prediction of the fermentation kinetics parameters with high coefficient of determination R2 values.Luedeking-Piret model for xanthan biopolymer production in three different concentration of sugar cane molasses (30, 60 and 90 g/l) as the sole carbon source substrate were studied. A good agreement between experimental and predicted values indicated that the unstructured models were able to describe this fermentation process successfully. The values of specific growth rate μ_max of logestic model for sugar cane molasses (30, 60 and 90 g/l) were 0.029, 0.031 and 0.032 h-1 respectively. The values of α and β is 5.280, 6.594, 8.518 and 0.072, 0.066, 0.086 respectively which shows that the xanthan production is growth associated since the value of the growth associated parameter α is much more than the value of nongrowth associated parameter β in Luedeking Piret model. Moreover, the values of γ and 𝜂 in modified Luedeking-Piret model were obtained.

Abstract This research work is concerned with the bioconversion of a heavy hydrocarbon cut from a petroleum refinery using native anaerobic consortia. The heavy cut is taken from one of the end-cuts of the vacuum distillation column of Tehran refinery which is normally fed into Isomax unit (a catalytic cracking process) called Isofeed. The consortia for this study were prepared from the petroleum-contaminated sludge and soils from Abadan, Shiraz, Isfahan and Tehran petroleum refineries of Iran. Nine microbial samples were collected (A, B, C, and I) and examined. Microorganisms were cultivated in an anaerobic medium to which Isofeed from Tehran refinery was added under anaerobic conditions. After twice sub-culturing the samples, the oil was separated from the liquid and examined to identify its bioconversion extent. For this
purpose, a column chromatograph method was used to separate saturates, aromatics and resins content of the oil. The results demonstrate that consortia A and C were able to increase the saturated and aromatics fractions of the oil and reduce the resins content of the oil. The saturated fractions of the bio-treated oil were also analyzed by a GC-MS analytical instrument. The GC-MS results revealed that the amount of normal chain hydrocarbons are reduced and the branched and cyclic hydrocarbons are increased.