Ana Aurelia Chirvase

Centrifugal partition extraction, a new method for direct metabolites recovery from culture broth: case study of torularhodin recovery from Rhodotorula rubra.

Centrifugal partition extraction (CPE), close to centrifugal partition chromatography, put in contact in a continuous way two immiscible liquid phases. This work presents early experiments on CPE use for solid-liquid-liquid extraction. It was applied to the direct treatment of culture broth for metabolites recovery. Torularhodin is one of the carotenoid pigments produced by the yeast Rhodotorula sp., with a terminal carboxylic group considered nowadays as a powerful antioxidant to be included in food and drugs formulations. Torularhodin was extracted from Rhodotorula rubra ICCF 209 cells by CPE. The recovery of torularhodin reaches 74 μg/g of biomass i.e. 294 μg/L of culture medium. The efficiency of the extraction step increased with the operating flow rate. The extraction yield could reach 91% with a contact time lower than 2 min. A 300 mL apparatus allowed a feed at 90 mL/min. The technique is proposed for extraction or sample preparation before analysis.

Optimal fed-batch bioprocess control. An advanced approach

Abstract Bioprocesses are appreciated as difficult to control because their dynamic behavior is highly nonlinear and time varying, in particular, when they are operating in fed batch mode. The research objective of this study was to develop an appropriate control method for a complex bioprocess and to implement it on a laboratory plant. Hence, an intelligent control structure has been designed in order to produce biomass and to maximize the specific growth rate.

Progress in Vegetable Oils Enzymatic Transesterification to Biodiesel - Case Study

These days the interest of fuels preparing from sustainable natural resources is continuously increasing due to the rising prices of the fossil fuels and the political instability in the oil producing countries. The fuels manufacturing from local vegetal resources can sustain the every country’ prosperity, including rural, agricultural, economically disadvantaged regions. Nowadays only the bioethanol and the biodiesel are already produced at industrial level from sustainable raw materials. The biodiesel is manufactured by the chemically catalysed transesterification of the triglycerides from the vegetable oils, rapeseed oil in Europe and soya oil in USA. As the methanol is often used as alcohol reagent, the reaction is consequently named methanolysis. The most applied catalysts are alkalines (especially NaOH) or mineral acids. So the biodiesel represents the methyl esters of the fatty acids from the vegetable oils. The present diesel engines can normally use a mixture of diesel with 5% v/v biodiesel. Biodiesel contains virtually no sulfur or aromatics, and use of biodiesel in a conventional diesel engine results in substantial reduction of unburned hydrocarbons, carbon monoxide and particulate matter. The production and use of biodiesel, compared to petroleum diesel, resulted in a 78.5% reduction in carbon dioxide emissions. Moreover, biodiesel has a positive energy balance. The chemical transesterification applied at industrial level has important advantages, but also limitations: in spite of the high conversion yields and the short reaction duration, the global transformation is energetically intensive, the glycerol recovery is difficult, the alkaline catalyst must be separated, the wastewaters are to be treated by a rather complex procedure, and both the free fatty acids and water can badly influence the reaction. These unfavourable situations can be diminished by performing the enzymatic transesterification on conditions that: (a) the immobilised lipase used as biocatalyst must be as cheap as possible; (b) one can obtain the economic efficiency of the whole biotransformation process similar to that characteristic to the chemical process, these objectives being presented function of the research methodology and results. The comparison between the chemical way and the enzymatic way is presented in the Table 1.