Fermentation isopropanol

Ethanol production in the fermentation process was detected with gas chromatography, HP 5890 series II (Hewlett-Packard, Avondale, PA, USA) equipped with a flame ionisation detector (FID) and GC column Porapak QS (Alltech Associates Inc., Deerfield, IL, USA) 100/120 mesh. The oven and detector temperature were 175 and 185 °C, respectively. Nitrogen gas was used as a carrier. Isopropanol was used as an internal standard. 

The mash from the Streptomyces aureofaciens fermentation broth is acidified and filtered. The filtrate is adjusted to the desired pH, usually 7-8.5, and various flocculating or chelating agents may be added (e.g., vinyl acetate-maleic anhydride copolymer, sodium EDTA, ammonium oxalate, Arquad). The precipitate is (1) stirred with filter aid, filtered, stirred with HC1, refiltered, mixed with 2-ethoxyethanol, filtered, washed, and the filtrates are combined, acidified with HC1, NaCl is added, and the crystals are collected, washed with 2-ethoxyethanol, water, and ethanol, and dried (67), or (2) extracted into methyl isobutyl ketone, the extracts are combined, filtered, and acidified with HC1, and the crystals are collected and washed with water, 2-ethoxyethanol, and isopropanol, and vacuum-dried. If the crystals are greenish, they are treated with sodium hydrosulfite at pH 1.8, filtered, washed, and dried as in (1) above (68). 

Another problem with fermentation products is often the limited outlet. The primary fermentation products such as alcohols require chemical transformations to convert them into species acceptable by the chemical industry as intermediates. This can normally occur through dehydration reactions [77]. For example, ethanol may need to be dehydrated into ethylene, isopropanol into propylene and n-butanol into n-butylene. These reactions are reversed petrochemical reactions and normally lead to products that have a lower selling price than the starting materials under the present structure of the chemical industry. For this reason, bioethanol is still used unchanged as an oxygenated gasoline additive. 

The crude paclitaxel is recovered from the rich aqueous fermentation broth by liquid/liquid extraction with a mixture of isobutyl acetate (IBA) and isopropanol (IPA), both class 3 solvents. The waste aqueous phase is stripped to remove residual organic solvents (IBA/IPA), treated with sodium hydroxide to deactivate any paclitaxel residues, and processed through a standard wastewater treatment facility. The amount of solid waste biomass generated in the process is negligible. 

The yield of ATP (31/ mol/mol of glucose) is the highest we have discussed giving an efficiency of 50%. Another fermentation yields butanol, isopropanol, ethanol, and acetone. 

The NADH is derived from glyceraldehyde 3-phosphate dehydrogenation. Thus, yeast fermentation yields ethanol rather than lactate as an end product of glycolysis. Small amounts of ethanol are produced by the microbial flora of the gastrointestinal tract. Other types of fermentation using similar reactions occur in microorganisms and yield a variety of products (e.g., acetate, acetone, butanol, butyrate, isopropanol, hydrogen gas). 

PS-60 is produced at a conversion efficiency of approximately 50% resulting in a very high viscosity fermentation beer (4000-8000 cP). It can be recovered from solution by precipitation with alcohol ( -i two volumes of isopropanol) to produce a fibrous percipitate. 

About 40 years after the ground-breaking studies of Louis Pasteur, anaerobic acetone production was described using a microorganism called at that time Paenibacillus macerans [3, 4]. At that time, isopropanol also was identified as a by-product of butanol fermentation by Pringsheim [5, 6]. 

Diirre, P. (1998) New insights and novel developments in clostridial acetone/butanol/isopropanol fermentation. Appl. Microbiol. Biotechnol, 49, 639 -648. 

Screenwashes were typically 50 50 methanol and water but now usually contain typically 10-50% isopropanol although some mixed propanols are also used (w-propanol and isopropanol). In a small number of formulations, ethanol is used in similar proportions to isopropanol. Ethanol is the favoured alcohol in the Scandinavian countries (Norway, Sweden and Finland) where prices of isopropanol and ethanol are comparable. Methanol is used in the USA, where price is the dominant factor. Some changes are taking place as formulations based on isopropanol/ethanol are now comparable in price to the normal 20-30% methanol-based systems. The green benefits of using ethanol from renewable fermentation sources is also causing a small but discernible shift. 

Lee J, Jang Y-S, Choi SJ, Im JA, Song H, Cho JH, Seung DY, Papoutsakis ET, Bennett GN, Lee SY. (2012). Metabolic engineering of Clostridium acetobutylicum ATCC 824 for isopropanol-butanol-ethanol fermentation. Appl Environ Microbiol, 78,1416-1423. 

Over the years the butanol or the other minor solvents became more important than the acetone, and the process continued to develop. Different species of clostridia were used to produce these other solvents (e.g. C. butylicum for butanol and isopropanol, and C. butyricum for butyric and acetic acids). Strains were isolated which made a very efficient use of molasses rather than starch. The pH of the medium was controlled by aqueous ammonia rather than by chalk, giving a completely soluble medium suitable for in-line sterilisation. The spent cells recovered at the end of the fermentation were found to be a good source of riboflavin (Vitamin B2), and, after drying, were used as a supplement to animal feeds. The carbon dioxide and hydrogen were collected and sold, and continuous distillation was developed for the solvent recovery. 

---