Producer gas, fermentation

For acetogens, such as the ones identified for producer gas fermentation, ethanol synthesis is reported to follow the Wood-Ljungdahl pathway. The overall stoichiometry for the formation of ethanol (C2H5OH) from CO, CO2, and H2 is... 

Continuous stirred-tank reactors (CSTRs) have been routinely employed for producer gas fermentations. A two-stage reactor system has also been used to maximize ethanol production and minimize the formation of byproducts. Carbon monoxide and hydrogen conversions of 90% and 70%, respectively, were observed in the first reactor, while they were about 70% and 10% in the second reactor. High ethanol-to-acetate ratios were achieved by the use of such a dual reactor system. Bubble colunms are also commonly used for industrial fermentations. A comparative study was performed between a CSTR and a bubble column reactor for CO fermentation using Peptostreptococcus productus. Higher conversion rates of CO were observed with the bubble column without the use of any additional agitation. Producer gas fermentation with packed bubble colunms and trickle bed reactors has also been studied. The trickle bed reactor has a low pressure drop and liquid hold-up, and the conversion rates were the highest compared to CSTRs and bubble columns. 

Fresh Samples. Fresh samples with adequate activity are canned without freeze-drying. However, they tend to ferment and produce gas, and the cans expand unless a preservative is added. At present we fill the cans with 200 grams of materials and add 5 cm.3 of undiluted formalin (40%) before sealing. The contents often expand very slightly, but since the swelling is not progressive, these cans also can be stored at room temperature indefinitely after counting. 

The carbon dioxide gas that is produced during fermentation is what makes yeast bread rise. When the bread is cooked, the heat gets rid of the carbon dioxide and alcohol that the yeast produced, leaving behind tiny holes where the carbon dioxide bubbles burst. These holes make the bread light and fluffy. 

Since the twenties and thirties butanol together with acetone was produced by fermentation of carbohydrates (corn). In the sixties the process was replaced by the hydroformylation of propene. In the OXO process alkenes react with synthesis gas in the presence of a homogeneous catalyst to give a mixture of branched and linear aldehydes ... 

Ether synthesis produces branched ethers like methyl t-butyl ether (MTBE) by reacting methanol (or ethanol) with branched alkenes such as isobutene. These ethers are valuable for their high octane quality and also, on account of the oxygen they contain, their ability to reduce both CO and hydrocarbon exhaust emissions. Alcohols, such as methanol, manufactured from natural gas or coal, and ethanol, produced by fermentation, are other oxygenated components in limited use. 

The symptoms of lactose intolerance are caused by the osmotic effect of the unabsorbed lactose, which increases water and sodium levels in the lumen. Unabsorbed lactose, upon reaching the colon, can be fermented by colonic flora, which produces gas, causing abdominal distension and discomfort. A lactose tolerance test has been developed based on the measurement of blood glucose level and the hydrogen level in the breath. However, its usefulness has been questioned as the test is based on a 50 g dose of lactose. 

Reich process. A method of purifying carbon dioxide produced in fermentation. The small amounts of organic impurities are oxidized and absorbed, and the gas is then dehydrated with chemicals. 

Yeast is added to glucose solution and it is allowed to ferment. C02 gas produced by fermentation clouds the Ca(OH)2 solution in the test tube. 

Acetic acid produced by fermentation does not involve toxic carbon monoxide or methanol, nor expensive rhodium. Products from petroleum or natural gas are cheaper because they do not include the cost of natural resource depletion or of global warming. (See Chap. 17 for a discussion of such costs.) It is also possible that application of some of the newer techniques will improve the fermentations so that they give better yields and are more cost-competitive. This is one of the keys to a sustainable future.19 Industrial research in this area is increasing.20... 

Thermoplastic poly(lactic acid) (PLA) is obtained by polycondensation of the acid or by ring-opening of the lactide. Its mechanical performance is similar to that of PS. Lactic acid (LA) can be produced by fermentation of coal, petroleum or namral gas. PLA is sensitive to enzymatic and chemical hydrolysis. It has been used for medical implants, dmg delivery, packaging and consumer goods. LA can be copolymerized with ethylene glycol into highly hydrophilic poly(ether-ester) block copolymers. Similarly, LA was copolymerized... 

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