Claims:We claim:
1. A composite process for the production of ethanol by yeast fermentation comprising:
(a) a first phase using a syrup stream followed by;
(b) a second phase using a bio-syrup stream followed by;
(c) a third phase using a molasses stream; and
(d) running said composite process for up to 360 days in a year.
2. The process as claimed in claim 1, wherein said syrup stream comprises fermentable sugars up to 50 % by weight.
3. The process as claimed in claim 1, wherein said syrup stream is obtained by evaporation of sugarcane juice.
4. The process as claimed in claim 1, wherein said bio- syrup stream comprises fermentable sugars up to 77 % by weight.
5. The process as claimed in claim 1, wherein said molasses stream is molasses B or molasses C.
6. The process as claimed in claim 1, wherein said molasses C comprises fermentable sugars up to 50 % by weight.
7. The process as claimed in claim 1, wherein said molasses B comprises fermentable sugars up to 60 % by weight.
8. The process as claimed in claim 1, wherein said bio-syrup stream is obtained by inversion of said syrup by treatment of between 4,00,000 and 10,00,000 INV units of invertase per metric ton of said syrup.
9. The process as claimed in claim 1, wherein said bio-syrup stream is obtained by inversion of said syrup with yeast invertase.
10. The process as claimed in claim 1, wherein said first phase is run between 40 and 80 days.
11. The process as claimed in claim 1, wherein said second phase is run between 160 and 200 days.
12. The process as claimed in claim 1, wherein said third phase is run between 90 and 120 days.
13. The process as claimed in claim 1, wherein said yeast is a Saccharomyces spp.
14. The process as claimed in claim 1, wherein said yeast is recycled to increase the efficiency of said composite process.
15. The process as claimed in claim 1, wherein said composite process has fermentation efficiency between 91 and 93 % and overall process efficiency between 89 and 91 % of ethanol from fermentable sugars.
, Description:FIELD OF THE INVENTION
The invention relates to a composite process for the production of ethanol using different types of sugary feed stocks for up to 360 days in a year. More particularly it relates to the use of bio-syrup obtained from sugarcane juice during the crushing season of the year and using it in off-season period for the production of ethanol.

BACKGROUND
The conventionally ethanol is produced from sugary feedstock like molasses, which is the by-product of sugar production industry. The molasses produced during sugarcane crushing season is stored and used during the off-season period for the production of ethanol. However, recent increase in the demand for ethanol as a vehicle fuel has lead to the direct use of sugarcane juice for the production of ethanol without extraction of table sugar from it. But this created a different problem as the sugarcane juice cannot be stored and required to be used immediately for the production of ethanol. Further it has between 10 and 14 % fermentable sugar requiring large volume of fermentation vessel due to diluted nature of said juice and subsequent larger distillation columns due to between 6 and 8 % titre of ethanol in the fermented wash. This problem may be solved by concentrating said juice up to 2-3 times and using it a feedstock. This concentrated juice is called syrup. But this still does not solve the problem of off-season requirement of said syrup as it is not stable and prone to crystallization of sucrose upon storage and contamination due to microorganisms. This limits its use as a feedstock in the off-season period for the production of ethanol. The conventional sugar and ethanol production is seasonal activity when from November to March (crushing season) the harvested sugarcane is available for the industry to make sugar and/or ethanol. Then in the off-season period ethanol is primarily produced using molasses. However, availability of molasses is not stable and demand exceeds the supply. Further the price of molasses increases during the off-season period leading to increase in the production cost of ethanol for bio-fuel applications.

The present invention provides a composite process for the production of ethanol from fermentable sugar containing feed stocks like molasses, syrup and bio-syrup that is much efficient in terms of ethanol recovery and whole year operation of the ethanol production plants. Further the method has several advantages over the conventional methods, further providing economic advantages to the use of the disclosed invention.

DETAILED DESCRIPTION OF THE INVENTION
In one embodiment of the disclosed invention, the bio-syrup is prepared from concentrated sugarcane syrup, which is obtained by evaporation of sugarcane juice by inverting it using the yeast invertase enzyme or acids. The bio-syrup is heavy, partially inverted cane syrup having value of about 85 ºBx. While said cane syrup is made from the concentration of sugarcane juice with about 50 ºBx by weight. The general composition of said bio-syrup is dependent on the cane juice from which it is made. A typical composition is as follows:
Parameter Value
ºBrix 85
Sucrose 21 % w/w
Inverted sugar 55 % w/w
Total fermentable
sugars 76 % w/w

In another embodiment of the disclosed invention, said bio-syrup is made after removing impurities and partially inverting sucrose using invertase enzymes or acids to glucose and fructose in said syrup and concentrating it further up to 85º Bx. It is necessary to invert sucrose to avoid it being crystallized or solidified in the storage tanks at high concentrations. The shelf life of bio-syrup so produced is up to 12 months, depending on storage and climatic conditions.

In one of the embodiment of the present invention, sugarcane syrup having from 40 to 45 % sucrose by weight is used as a starting material. The said syrup is mixed with between 4,00,000 and 10,00,000 INV units of yeast invertase per metric ton of syrup for inversion reaction. Then this mixture is allowed to react for between 6 and 8 hours at 60 to 65 0C. Next, said reaction mass is further concentrated to about 85 ºBx by evaporation and cooled to room temperature and then analysed by the high performance liquid chromatography to check the sugar composition. The final bio-syrup stream contained between 72 and 78 % of fermentable sugars by weight having between 50 and 55 % inverted sugar by weight.
In one of the embodiment of the present invention, to run the ethanol production plant for up to 360 days, in the first phase about 9,500 to 10,500 MT of syrup as such, syrup having about 55 ºBx of solid is used for 42 days to produce about 70 KLPD of ethanol using about 230 MT of said syrup per day. In the second phase between 29,000 and 31,000 MT of bio-syrup is used for 195 days to produce about 70 KLPD of ethanol using about 155 MT of said bio-syrup per day. In the third phase between 23,000 and 24,000 MT of molasses B produced about 60 KLPD of ethanol when about 185 MT of molasses B is used per day and afforded said plant to run further for about 120 days. Herein, said molasses B contained fermentable sugar at about 60 % by weight.
In one of the embodiment of the present invention, to run the ethanol production plant for 360 days, in the first phase about 9,500 to 10,500 MT of syrup as such, syrup having about 55º Bx of solid is used for 42 days to produce about 70 KLPD of ethanol using about 230 MT of said syrup per day. In the second phase between 29,000 and 31,000 MT of bio-syrup is used for 195 days to produce about 70 KLPD of ethanol using about 155 MT of said bio-syrup per day. In the third phase between 23000 and 24000 MT of molasses C produced about 50 KLPD of ethanol when about 200 MT of molasses C is used per day and afforded said plant to run further for about 120 days. Herein, said molasses c contained fermentable sugar at about 50 % by weight.
In another of the embodiment of the present invention, the fermentation is carried out using a yeast from the group of Saccharomyces spp, and more specifically Saccharomyces cerevisiae, which is pre-cultured in a pre-fermenter and then mixed with the fermentation medium. To increase the overall efficiency of the ethanol production process, the yeast is separated from the fermented wash by gravity settlement or centrifugation, and recycled to the fermentation medium. Further, another strain of yeast Saccharomyces cerevisiae that used for the fermentation process is gravity settling type when not in suspension during agitation. It is separated in a gravity settling tank from the fermented wash and recycled to increase the overall efficiency of the fermentation process.
Examples provided below give wider utility of the invention without any limitations as to the variations that may be appreciated by a person skilled in the art. A non-limiting summary of various experimental results is given in the examples, which demonstrate the advantageous and novel aspects of the method of using low amounts of the yeast invertase enzyme for the preparation of bio-syrup.

EXAMPLE 1
A batch of about 250 kg fresh sugarcane juice was subjected to evaporation to obtain about 70 kg of concentrated cane syrup having about 55 ºBx of solids, which contained about 42 % sucrose by weight and about 4 % inverted sugar by weight. The initial pH of said syrup was about 5. This syrup was mixed with about 0.8 g of yeast invertase enzyme having specific activity of about 52,000 INV units and treated at about 55 0C for about between 8 and 12 hours allowing the inversion of sucrose to invert sugar to take place. Next, said treated syrup was cooled to room temperature and analysed by HPLC to check the sugar types in it. It contained about 46 % total sugar by weight, about 14.5 % sucrose by weight and about 16.5 % glucose by weight plus about 16.5 % fructose by weight, i.e., about 47.5 % inverted sugar by weight. This method afforded more between 65 and 70 % inversion of sucrose to invert sugar and this stream was called invert syrup.

EXAMPLE 2
A batch of about 100 kg of invert syrup having about 55 ºBx of solids was used as the feedstock, which contained about 45 % invert sugar by weight. The initial pH of said syrup was about 5. This syrup was subjected to evaporation at about 60 0C under vacuum and concentrated till about 85 ºBx of solids were achieved in it. This concentrated invert syrup is called bio-syrup and was stored effectively for the off-season use without any degradation in it sugar contents upon storage for up to 12 months. Further, due to invent sugar present in said bio-syrup, the crystallisation of the sugar molecules is inhibited during longer periods of storage. Further, said bio-syrup is safe from microbial degradation as the high sugar content prevents the growth of microbes due to lack of water activity associated with it.

EXAMPLE 3
A sugar production plant with a crushing capacity of about 5,000 MT per day, operating for about 120 days of the sugarcane crushing season produced between 23,000 and 24,000 MT of molasses C after routine extraction of sugar. This molasses C produced about 50 KLPD of ethanol when about 200 MT of molasses C was used per day and afforded said plant to run for about 120 days. On the other hand, said sugar plant produced between 35,000 and 36,ooo MT molasses B after routine extraction of sugar. This molasses B produced about 60 KLPD of ethanol when about 190 MT of molasses B used per day and afforded said plant to run for about 190 days.

EXAMPLE 4
A sugar production plant with a crushing capacity of about 5,000 MT per day, operating for about 120 days of the sugarcane crushing season produced between 1,53,000 and 1,54,000 MT of cane syrup having about 55º Bx of solids. Of this syrup about 11,000 to 12,000 MT of syrup as such is used for about 50 days to produce about 70 KLPD of ethanol using about 240 MT of said syrup per day. Next, between 57,000 and 58,000 MT of said syrup is used to convert it to between 37,000 and 38,000 MT of bio-syrup. Then said bio-syrup is used for about 240 days to produce about 70 KLPD of ethanol using about 155 MT of said bio-syrup per day. This plant further produced between 13,000 and 15,000 MT of molasses C. Next, said molasses C produced about 50 KLPD of ethanol when about 200 MT per day was used and afforded said plant to run further for about 70 days.

EXAMPLE 5
A sugar production plant with a crushing capacity of about 5000 MT per day, operating for about 120 days of the sugarcane crushing season produced between 1,52,000 and 1,54,000 MT of cane syrup having about 55º Bx of solids. Of this syrup about 9,500 to 10,500 MT of syrup as such was used for about 42 days to produce about 70 KLPD of ethanol using about 230 MT of said syrup per day. Next, between 47,000 and 48,000 MT of said syrup was used to convert it to between 30,000 and 31,000 MT of bio-syrup. Then said bio-syrup was used for about 195 days to produce about 70 KLPD of ethanol using about 155 MT of said bio-syrup per day. This plant further produced between 23,000 and 24,000 MT of molasses B. Next, said molasses B produced about 60 KLPD of ethanol when about 185 MT per day was used and afforded said plant to run further for about 120 days.

EXAMPLE 6
For the production of ethanol in an ethanol plant having the capacity of 50 KLPD, about 198 MT of molasses C containing about 45 % by weight of fermentable sugar was used to prepare the fermentation medium. This medium was supplemented with routine salts and nutrients for the effective growth of the yeast. The volume of medium was adjusted to about 536 m3 with fresh water along with pre-fermented starting culture, to obtain the final ethanol titre of about 9 % by volume. After completion of the fermentation, the fermented wash was subjected to the distillation process to obtain about 50 KLPD of ethanol of about 99.8 % purity. This process afforded the fermentation efficiency of about 89 % and overall efficacy of about 87 % ethanol from the fermentable sugar.

EXAMPLE 7
For the production of ethanol in an ethanol plant having the capacity of 50 KLPD, about 160 MT of molasses B containing about 55 % by weight of fermentable sugar was used to prepare the fermentation medium. This medium was supplemented with routine salts and nutrients for the effective growth of the yeast. The volume of medium was adjusted to about 425 m3 with fresh water along with pre-fermented starting culture, to obtain the final ethanol titre of about 12 % by volume. After completion of the fermentation, the fermented wash was subjected to the distillation process to obtain about 50 KLPD of ethanol of about 99.8 % purity. This process afforded the fermentation efficiency of about 90 % and overall efficacy of about 88 % ethanol from the fermentable sugar.

EXAMPLE 8
For the production of ethanol in a plant having the capacity of 50 KLPD, about 174 MT of syrup containing about 50 % by weight of fermentable sugars (with about 55 ºBx of solids) was used to prepare the fermentation medium. This medium was supplemented with routine salts and nutrients for the effective growth of the yeast. The volume of medium was adjusted to about 425 m3 with fresh water along with pre-fermented starting culture, to obtain the final ethanol titre of about 12 % by volume. After completion of the fermentation, the fermented wash was subjected to the distillation process to obtain about 50 KLPD of ethanol of about 99.8 % purity. This process afforded the fermentation efficiency of about 91 % and overall efficacy of about 89 % ethanol from the fermentable sugar.

EXAMPLE 9
For the production of ethanol in an ethanol plant having the capacity of 50 KLPD, about 116 MT of bio-syrup containing about 75 % by weight of fermentable sugars (with about 85 ºBx of solids) was used to prepare the fermentation medium. This medium was supplemented with routine salts and nutrients for the effective growth of the yeast. The volume of medium was adjusted to about 425 m3 with fresh water along with pre-fermented starting culture, to obtain the final ethanol titre of about 12 % by volume. After completion of the fermentation, the fermented wash was subjected to the distillation process to obtain about 50 KLPD of ethanol of about 99.8 % purity. This process afforded the fermentation efficiency of about 91 % and overall efficacy of about 89 % ethanol from the fermentable sugar.

EXAMPLE 10
For the production of ethanol in an ethanol plant having the capacity of 50 KLPD, about 170 MT of syrup containing about 50 % by weight of fermentable sugars (with about 55 ºBx of solids) was used to prepare the fermentation medium. This medium was supplemented with routine salts and nutrients for the effective growth of the yeast. The volume of medium was adjusted to about 425 m3 with fresh water along with pre-fermented starting culture, to obtain the final ethanol titre of about 12 % by volume. However, in this case the yeast used was of a granulating gravity settling yeast that was collected in a gravity settling tank after completion of fermentation and removed for recycling. The clarified fermented wash was subjected to the distillation process to obtain about 50 KLPD of ethanol of about 99.8 % purity. This process afforded the fermentation efficiency of about 93 % and overall efficacy of about 91 % ethanol from the fermentable sugar.

EXAMPLE 11
For the production of ethanol in an ethanol plant having the capacity of 50 KLPD, about 114 MT of bio-syrup containing about 75 % by weight of fermentable sugars (with about 85 ºBx of solids) was used to prepare the fermentation medium. This medium was supplemented with routine salts and nutrients for the effective growth of the yeast. The volume of medium was adjusted to about 425 m3 with fresh water along with pre-fermented starting culture, to obtain the final ethanol titre of about 12 % by volume. However, in this case the yeast used was of a granulating gravity settling yeast that was collected in a gravity settling tank after completion of fermentation and removed for recycling. The clarified fermented wash was subjected to the distillation process to obtain about 50 KLPD of ethanol of about 99.8 % purity. This process afforded the fermentation efficiency of about 93 % and overall efficacy of about 91 % ethanol from the fermentable sugar.

EXAMPLE 12
For the production of ethanol in an ethanol plant having the capacity of 50 KLPD, about 114 MT of bio-syrup containing about 75 % by weight of fermentable sugars (with 85º Bx of solids) was used to prepare the fermentation medium. This medium was supplemented with routine salts and nutrients for the effective growth of the yeast. The volume of medium was adjusted to about 425 m3 with fresh water along with pre-fermented starting culture, to obtain the final ethanol titre of about 12 % by volume. However, in this case the yeast used was collected by centrifugation after completion of fermentation and removed for recycling. The clarified fermented wash was subjected to the distillation process to obtain about 50 KLPD of ethanol of about 99.8 % purity. This process afforded the fermentation efficiency of about 93 % and overall efficacy of about 91 % ethanol from the fermentable sugar.

The several advantages of the disclosed invention are listed below:
1. The quality of bio-syrup obtained by disclosed method is superior as other impurities like caramel, HMF, furfural, etc formation is substantially reduced.
2. The bio-syrup is viscous material with high solids, with very low water activity and practically not prone to the growth of microbes and is preserved well with any deterioration of its quality.
3. The bio-syrup is easy to store for longer period for the off-season uses without significant loss of fermentable sugars in it.
4. By way of using bio-syrup as a feedstock for the production of ethanol in the off-season period the capacity of the ethanol production plant may be optimally used and it may be operated for up to 360 days in the year.
Embodiments provided above give wider utility of the invention without any limitations as to the variations that may be appreciated by a person skilled in the art. A non-limiting summary of various embodiments is given above, which demonstrate the advantageous and novel aspects of the process disclosed herein.