IE59108B1

IE59108B1 - Microbial production of ethanol

Info

Publication number: IE59108B1
Application number: IE35686A
Authority: IE
Original assignee: Mccormack Christopher Alphonsu
Priority date: 1986-02-07
Filing date: 1986-02-07
Publication date: 1994-01-12
Also published as: GB8702761D0; GB2186289A; IE860356L; GB2186289B

Abstract

A process for producing ethanol from non-cultivated species of graminae which involves heating homogenized grass or hay with a ???-cellulase to convert cellulose to glucose, filtering the reaction medium following said treatment and subjecting the filtrate to fermentation with an ethanol-producing microbial system. The homogenized grass or hay may be hydrolysed with an inorganic acid or base before treatment with ???-cellulase. The ethanol may be used as fuel for an internal combustion engine.

Description

This invention relates to © process for producing ethanol from non-cultivated species of graminae ana to the use of the ethanol so produced as a fuel for an internal combustion engine» The use of ethanol as an alternative to fossil fuels to power the internal combustion engine has been proven and is well documented (c.£.„ A Step to Energy Independence; T.P. Lyons,» Alltech 1981; Gasohol for Energy Production; W-P. Cheremisinoff» Ann Arbor Science 1979)« Considerable data is available on the production of ethanol and its properties (c-f. Alcohols? Their Chemistry? Properties and Manufacture; ,J.A. Konick? Re inhold Book Corporation? 1968). With th® discovery o£ the ensvsa© cellules© in 1899 by KacFayden ®nd Bloxell? it became possible to produce ethanol enzymatically by the fermentative production of ethanol fro» cellulosic material. According to this process the cellulose is first converted to glucose and then through fermentation to ethanol.

Various cellulosic materials have been used to produce ethanol by chemical or enzymatic processes or by a combination of said processes. Such materials induce wood? wheat straw (Biotechnology and Bieengineering (U.S-A.) 1984 Vol. 26 No. 9 p 1122-1125) and rice straws . ; (Enzyme and Hicrobial Technology (England) 1985 Vol. 7 No. 3 p 115-120)., Th© use of Kallar grass for the production of ethanol is reported in the Pakistan Journal r &i Botany (Pakistan) 1982 Vol. 14? No. Spec» Issue p ^3- < There is bo report of son-cultivated specie® og gr&min&e (grasses) being used to produce ethanol oa a commercial scale, Mon-cultivated grass is in plentiful '*> supply and is a very cheap raw material, f 5 it is an object of the present invention to produce ethanol from non-cultivated species ©f graminae in high yield and to use the'ethanol so produced as an alternative to fossil fuels.

Accordingly, the invention provides a process of 1 θ producing ethanol from non-cultivated species of graminae which comprises the steps of; a) homogenising the grass.· b) rendering the cellulose in the homogenized grass susceptible to attack by - cellulase toy hydrolysing the homogenised grass with an inorganic tease? c) reacting the thus treated grass with ,/S - cellulase so as t© convert the cellulose in the grass to glucose? d) filtering the reaction medium? ©> fermenting the filtrate with an ethanol - produeing microbial system; f) separating the ethanol thus produced.

Preferably, the microbial system is a yeast, more 25 especially a yeast of the genus saccharomyces cerevisiae;.

A particularly preferred yeast is baker's yeast. preferably, the cellulose ia the grass is rendered susceptible to attack toy fi - cellulase by hydrolysing the homogenised grass with the inorganic base and boiUng thi® mixture. An ©specially preferred base is sodium hydroxide.

The grass may be freshly cut grass ©r hay.

Xn the homogenisation step, the grass is optionally moistened with water* However, when the grass used is in the fori® of hay tb© addition of water will normally toe necessary.

Further, preferably, the homogenization ot th© grass is carried out in a pulp mill® The ethanol separated in step f, of the process according to the invention is purified by distillation in conventional manner® Similarly, the fermentation step e) with the microbial system is carried out in conventional manner® The ethanol produced by the process according to the invention can be used either as a fuel additive,, for example, 50/50 ethanol/petrol or 25/75 ethanol/petrol. Alternatively, the ethanol produced according to the process of the invention can be used as a complete replacement fuel. However, in the latter case, it is necessary to add mineral elements to the ethanol to reduce friction, static and wear in the engine® Such mineral elements include zinc, iron and cadmium. The mixture used as the fuel will depend on the conditions of carburation, purity of the ethanol, and the size of engine being fueled. To burn a mixture with a-high percentage of ethanol the carburettor of commercially available engines must be modified to allow optimum vapourization of the fuel, as hereinafter described.

Generally, this modification involves a constriction of the typical inlet' jet on any of the more basic carburettor units, such as the Solex (Trademark) carburettor, but would necessitate the replacment of more advanced types of carburettor units, such as ®feber units® The modification required in each case ie specific to the carburettor type.

The invention will be further illustrated with reference to the following description of embodiments thereof with particular reference to the accompanying , examples. ί EXAMPLE 1 Product ion of ethanol On© bale of freshly cut grass was homogenized in a pulp mill. To the grass pulp was added sufficient IN NaOH at 25°C to yield a suspension ©f th® grass in the NaOH. The resultant suspension was boiled under reflux at 100°C for one hour, cooled to 37°c and the pH brought to 5 using HCl», The mixure was then filtered and a solution of 8-cellulase (5 g/ml) added thereto. The suspension was incubated at 37°C for twelve hours. The Scellulase was obtained from Bio-Con Limited, Carrigaline, County Cork, Ireland. After the S-eellulase digestion the suspension was filtered. The cellules© was extracted for reuse in further cellulose digestion. The filtrate was then fermented with baker’s yeast ©t a concentration of 0»5 g/ml to produce ethanol® The ethanol thus produced was separated off and purified by distillation in conventional manner™ The yield of ethanol was 3 gallons per bale of freshly cut grass.

EXAMPLE 2 Ose of ethanol, to power an internal combustion engib® The ethanol produced in Example 1 was used as a replacement fuel in a modified 1500 cc internal combustion engine from a volkswagon Beetle 196S model.

The engine in question had been driven on normal petrol for some eleven years to a mileage <©>£ 30,000 miles (both engine and carburettor were therefor® well tested® A number of problems are encountered in using ethanol in a convention©! interned combustion engine.

For example, the timing of the engine must be reset, i.e. differently to manufacturers8 specified settings® Similarly, tappets, etc, must be adjusted to suit the new fuel» The major modification» however» on ©nv ·>».«, » . * previously petrol powered engine, will be that of the carburettor * The conventional carburettor is designed tovapouv<^ petrol, a liquid fuel which boils at about 23°C.

Ethanol on the other hand boils at ® much higher temperature. Xn order to overcome this problem two alternative modifications may be used: a) one can make the carburettor more efficient at vapourizing the fuel? or to) the fuel can be vanned before entering the inlet jets.

To make the carburettor more efficient at vapourizing the ethanol» the vapourizing jets on the Solex carburettor model; 30 PICT*, from the Volkswagon engine were made finer. in this regard» two methods '-'see employed - the first was to simply constrict the inlet jets» the second was to occlude the jets using a solder mad® of an alloy of tin and zinc» the sort normally used by ©n electrician. The purpose of both modifications was to produce a finer jet of fuel than normal, such that a greater proportion of the ethanol would be vapourised» To undertake the modifications the carburettors (two) were t.aken from the Volkswagen engine.

In order to carry out the first modification constriction - th© jets were mechanically constricted, the carburettor remounted on th© engine and the unit started on ethanol produced In Example 1. Smooth running of th© engine was obtained for some six minutes on 10 ml of ethanol» In the second modification - occlusion - again the engine wag tested running on the ethanol produced in f Example 1. The occlusion method is of importance since some modern carburettors do not have conventional inlet - jets, for example» the S.O- carburettor type, commonly - 6 employed by British Leyland to supply some of their mo®·© popular models» For carburettor models where constriction is required, it is also proposed to us® a small tetlon limed brass washer which would fit most types of carburettor jet where constriction is possible. For occlusion it is also proposed to use an electrostatic lining process for the jets.

It will be appreciated from the above description 10 that the process according to the invention would have considerable economic advantages, the principal one being a readily available cheap source of raw material for the production of ethanol.

Ethanol is already used in many countries in South 15 America as en alternative to fossil fuels.

Claims

1. CLAIMS χ„ A process for producing ethanol from non-cultivated species of graminae which comprises the steps of: f a) homogenizing the grass; ' k 5 b) rendering the cellulose in the homogenized grass susceptible to attack by fi- cellulase by hydrolyzing the homogenized grass with an inorganic base; c) reacting the thus treated grass with ficellulase so as to convert the cellulose in th® 10 grass to glucose; d) filtering the reaction medium; e) fermenting the filtrate with an ethanol-producing microbial system; f) separating the ethanol thus produced. 15 2. A process according to Claim 1, wherein the ethanolproducing microbial system is a yeast™ 3. A process according to Claim 2, wherein the yeast is of the genus Saccharomyces cereyisiae. 4. A process according to assy preceding claim, wherein

2. O the cellulose in the grass is rendered susceptible to attack by - cellulase by hydrolyzing the homogenised grass with -the inorganic base and boiling th® mixture thereby obtained.

3. 5. A process according to Claim 4, wherein the base is 25 sodium hydroxide. r fi. A process according to any preceding Claim, wherein the grass is freshly oat grass or hay.

4. 7. A process according to Claim S„ wherein the grass or hay is moistened with water.

5. 8. Ά process according to any preceding claim, wherein the homogenization of the grass is carried out in a pulp mill.

6. 9. A process according to any preceding claim j further 5 comprising purifying the separated ethanol toy distillation»

7. 10. A process according to Claim 1 for producing ethanol, substantially as hereinbefore described with particular reference to Example 1 of the accompanying Sxam10 pies.

8. 11» Ethanol whenever produced toy a process claimed in any one of Claims 1 to 10 for use as a fuel for an internal combustion engine.