GB2113711A

GB2113711A - Production of alcohol by continuous fermentation

Info

Publication number: GB2113711A
Application number: GB08209257A
Authority: GB
Inventors: Kenji Kida; Shigeru Morimura
Original assignee: Hitachi Zosen Corp
Current assignee: Hitachi Zosen Corp
Priority date: 1982-01-26
Filing date: 1982-03-30
Publication date: 1983-08-10
Also published as: BR8201866A; ATA125882A; GB2113711B; PH21258A; JPS58129979A; AT383827B

Abstract

In a process for producing ethyl alcohol from a sugar by continuous fermentation using a fermentation apparatus of the fluidized bed type, bacteria having ability to effect alcoholic fermentation are deposited on a carrier which is fluidized.

Description

SPECIFICATION Process for producing alcohol by continuous fermentation Background of the Invention The present invention relates to a process for producing alcohol by continuous fermentation, and more particularly to a process for producing ethyl alcohol by continuously incubating bacteria in a fluidized state as deposited on a carrier.

In recent years, attention has been directed to alcohol which is prepared not petrochemically but fermentation for use as an energy source substituting for petroleum. The alcohol is produced from sugarcane, molasses obtained therefrom, potatoes, sweet potatoes, corn or like cellulosic or starch material by fermenting the material through the action of microorganisms.

With this process, the productivity of alcohol is through to be dependent on the concentration of microorganisms in the culture. To increase the concentration of microorganisms, therefore, research has been conducted, for example, on a method of circulating a concentrated culture of microorganisms and on a method which uses multiplication yeasts immobilized by being entrapped in substances of the polysaccharide type. With the former method, however, the centrifugal separator used for concentrating the culture becomes clogged up due to the presence of solid materials in the culture, presenting increasing difficulty in circulating the microorganisms and consequently entailing the necessity of washing the separator periodically.

Thus the method is very cumbersome to practice.

The latter method involves many technical difficulties to overcome for the quantity production of alcohol on a commercial scale.

Summary of the Invention In view of the above problems, an object of the present invention is to provide a process for producing alcohol with a greatly improved efficiency with use of a culture of microorganisms in an increased concentration.

Another object of the invention is to provide a process for producing alcohol which assures savings in the power for operating the fermentation apparatus used for the process.

To fulfill these objects, the present invention provides a process for producing alcohol by continuous fermentation comprising fluidizing bacteria deposited on a carrier and having ability to effect alcoholic fermentation with use of a fermentation apparatus of the fluidized bed type.

Brief Description of the Drawings Fig. 1 is a diagram showing a fermentation apparatus embodying the invention; and Fig. 2 is a graph showing the relation between the material dilution ratio and the productivity of alcohol determined with use of the embodiment.

Description of the Preferred Embodiment The process of this invention for producing alcohol is practiced with use of a fermentation apparatus of the fluidized bed type to assure savings in the power needed for fluidizing the bacteria deposited on a carrier and to prevent the wear and damage of the carrier.

Examples of useful carriers for depositing bacteria thereon are fired or non-fired vermiculite powder, active carbon, zeolite, etc. These materials can be effectively fluidized as admixed with cultures. Especially vermiculite powder, which is in the form of very thin flakes, is readily dispersible in the culture and highly resistant to wear and has a large specific surface area to permit deposition of a large quantity of bacteria thereon.

Examples of useful strains of bacteria having ability to effect alcoholic fermentation are those having such ability and belonging to the genus Zymomonas, especially Zymomonas mobilis. Such bacteria are described under the title "The Biology of Zymomonas" in Bacteriological Review, Vol. 41 No. 1, pp. 1 to 46. The above-mentioned species of bacteria readily deposits on the carrier spontaneously. Any strain of bacteria having ability to effect alcoholic fermentation is usable insofar as the bacteria have good ability to deposit on the carrier spontaneously. Culture media and fermenting conditions usually used for producing alcohol from sugars can be employed for the present process. The fermentation is carried out at a temperature of 25 to 320C, preferably about 300C, and at a pH of 4 to 6, preferably about 5.

The material to be fermented is supplied at a dilution ratio (supply of material/actual capacity of fermentation apparatus) of 0.2 to 0.6 h-1, preferably 0.3 to 0.5 h-1.

Examples of useful sugars are glycose, sucrose, galactose, etc.

According to this invention, the bacteria deposited on the carrier are fluidized in a fermentation apparatus of the fluidized bed type, consequently increasing the concentration of bacteria in the culture to produce alcohol from a sugar in improved yields. The use of the apparatus of the fluidized bed type assures savings in the power of fluidizing the bacteria on the carrier and also serves to prevent wear on the carrier. Further the use of the carrier provides increased solid surface areas for the deposition of bacteria. This also increases the concentration of bacteria in the culture to achieve an increased yield.

EXAMPLE Fig. 1 shows the fermentation apparatus of the fluidized bed type used. The apparatus consists chiefly of a fluidizing portion 1 in the form of a column 70 mm in inside diameter and 2000 mm in height, a settling portion 2 positioned at the top of the portion 1 and having an inside diameter of 140 mm, and a gas separating portion 3 inside the settling portion 2. The fluidizing portion 1 is externally provided with water jackets 4 by which the temperature of the portion 1 is controlled. The fluidizing portion 1 has an alkali injecting pipe 5 for controlling the pH of the fluid in the portion 1.

The apparatus is further provided with a water circulating pipe 6, temperature controllingrecording devices 7, temperature indicatingrecording devices 8, pH indicating-recording devices 9, a pH controlling-recording device 10, oxidation-reduction potential recorders 11, a cooler 12 and an air chamber 13.

The interior of the fermentation apparatus was washed with about 10 vol. % of ethanol solution first. A culture medium of the following composition was prepared.

Glycose 150 gel Yeast extract 3 g/I KH2PO4 1 9/1 (NH4)2So4 1 9/1 MgCl2. 6H20 0.5 g/l Defoaming agent 0.3 g/l (product of Toshiba Silicon Co., Ltd.) Fired or baked vermiculite powder (60 to 80 mesh) was added to the medium in an amount of 5 wt./vol. %. The resulting medium was sterilized by heating. A portion of the medium was used for incubating Zymomonas mobilis ATCC (the American Type Culture Collection) Deposition No. 10988. Five liters of the culture obtained and a 5-liter portion of the sterilized carrier-containing medium were placed into the fermentation apparatus, and the bacteria were incubated at a pH of 5 and temperature of 300C for about 8 hours.

Subsequently glycose serving as the material to be fermented was continuously supplied to the apparatus from a tank 14, while the sterilized medium (free from glycose) was also continuously supplied to the apparatus from a tank 1 5 at a specified rate so that the mixture contained the glycose material in a concentration of 1 50 g/l. The material was continuously fermented under the above conditions. The reaction mixture was introduced into the apparatus from its bottom and run off from its top and circulated through the apparatus via a pipe 1 6. To assist the carrier in flowing, the linear velocity of the reaction mixture was adjusted to 0.2 cm/sec by a diaphragm pump 1 7 on the circulating pipe 1 6.The rates of supply of the material and the medium were thereafter increased stepwise (glycose concentration: 150 g/l), and the ethanol concentration of the reaction mixture was measured at the varying supply rates.

Fig. 2 shows the relation between the material dilution ratio (rate of supply of material/actual capacity of apparatus) and the productivity of alcohol. The drawing shows an ethyl alcohol productivity of as high as about 23 g/l h at a dilution ratio of 0.4 h-1. Although the apparatus was continuously operated for about 2 months, no wear occurred on the carrier. Reportedly, the conventional continuous fermentation process wherein no carrier is used for the deposition of bacteria achieves an ethyl alcohol productivity of 2 to 3 g/l h. Thus the present invention achieves a remarkable improvement in the productivity of alcohol.

Claims

1. A process for producing alcohol from a sugar by continuous fermentation comprising fluidizing microorganism deposited on a carrier and having ability to effect alcoholic fermentation with use of a fermentation apparatus of the fluidized bed type.

2. A process as defined as claim 1 wherein the microorganism are a strain of the genus Zymomonas.

3. A process as defined in claim 1 wherein the microorganism are the strain of Zymomonas mobilis ATCC Deposition No. 10988.

4. A process as defined in claim 1 wherein the carrier is fired vermiculite powder

5. A process for producing alcohol substantially as hereinbefore described with reference to the accompanying drawings.