Greener Industry - Ethanol - Production Method 3

Limitations of conventional yeast
Yeast is very good at converting glucose, and other six-carbon sugars into ethanol. Unfortunately, a significant proportion of waste biomass consists of complex natural polymers made from sugars that are not "digested" readily by yeast enzymes.
These include hemicellulose, which on hydrolysis produces a range of sugars including: mannose, xylose, arabinose and galactose, depending on the original source.

Commercial Development

The BC International Corporation is attempting to develop this approach commercially in the United States, focusing on:

areas where legislation prohibits burning of agricultural waste
conventional ethanol plants suitable for conversion and refurbishment

KO11
A genetically modified bacterium, developed by the microbiologist Lonnie Ingram in 1987, has enabled these sugars to be converted to ethanol. The bacterium, referred to as KO11, would normally produce acids, but the modification means ethanol is produced instead.

The advantage over yeast is that a wider range of sugars can be processed, enabling the utilisation of biomass waste such as wood waste, corn stalks, rice hulls, and other organic waste, which would otherwise require disposal by some other method, or which could only be partially utilised by conventional fermentation methods, making them uneconomic.

Answer

a) the reaction rate is too slow b) at higher temperatures the enzymes start to denature and lose efficiency c) aerobic respiration will occur producing carboxylic acids in this case ethanoic acid (vinegar) d) ethanol is toxic to the enzymes in higher concentrations.