132 Fermentation and Biochemical Engineering Handbook Catabolite repression, transient repression and catabolite inhibition regulate the utilization of many carbohydrates. I Catabolite repression is a reduction in the rate of synthesis of certain enzymes in the presence of glucose or other easily metabolized carbon sources. In addition to this repression during steady-state growth in glucose, a period of more intense repression may occur immediately after the cells have been exposed to very high levels of glucose. This effect may last up to one generation or until glucose levels have been reduced to more acceptable levels. This is transient repression Catabolite inhibition is a control exerted by glucose on enzyme activity rather than on enzyme formation, analogous to the feedback inhibition in biosyn thetic pathways. enzymes involved in the utilization of other carbohydrates are inhibited by glucose o.. Simple sugars are available in powder or in liquid form and in a variety of purities. Glucose is usually made from corn starch through hydrolysis and sucrose from sugar cane or sugar beets. Sucrose is most often purchased in the form of molasses. Sugar beet molasses is the main by-product of table sugar production. Blackstrap molasses is the remaining by-product of raw sugar production from sugar cane, it is the prevailing type of cane molasses High test molasses or inverted cane syrup is a by-product of the refineries in which raw sugar is refined into white ortable sugar. Both blackstrap and beet molasses are widely used in the fermentation industry. Their approximate composition differs considerably, as indicated in Table 3. 5] The data on sugar beet molasses are averages from two ( 2) samples each of Dutch and French molasses from the 1990 campaign(column A). The Us beet molasses data are averages from five(5)factories belonging to American Crystal Sugar over the 1991 season( Column B). The blackstrap molasses data ar averages from several samples from Brazil, Dominican Republic and Haiti over the period 1975-1983. Table 4 is an indication of how complex a edium blackstrap molasses is. Upon diluting to 25%%, it was stripped under reduced pressure(40 mm Hg )at 38%C. The distillate was extracted with an ether/pentane(1: 1)mixture. Separation and identification was done with a capillary column and mass spectrometer. 5) Molasses is produced through nonsugar accumulation during the sugar production process and the accompanying increased solubility of sucrose. Of the non-sugars, the mineral salts have a much greater influence on sucrose olubility than the organic compounds. As a rule of thumb, one gram of mineral salts present in normal molasses will retain five grams of non- crystallizable sucrose. Through chromatographic separation processes, it is possible to recover up to approximately 85 percent of this sucrose
132 Fermentation and Biochemical Engineering Handbook Catabolite repression, transient repression and catabolite inhibition regulate the utilization of many carbohydrates.['] Catabolite repression is a reduction in the rate of synthesis of certain enzymes in the presence ofglucose or other easily metabolized carbon sources. In addition to this repression during steady-state growth in glucose, a period of more intense repression may occur immediately after the cells have been exposed to very high levels of glucose. This effect may last up to one generation or until glucose levels have been reduced to more acceptable levels. This is transient repression. Catabolite inhibition is a control exerted by glucose on enzyme activity rather than on enzyme formation, analogous to the feedback inhibition in biosynthetic pathways. Enzymes involved in the utilization of other carbohydrates are inhibited by glucose. Simple sugars are available in powder or in liquid form and in a variety of purities. Glucose is usually made from corn starch through hydrolysis and sucrose from sugar cane or sugar beets. Sucrose is most often purchased in the form of molasses. Sugar beet molasses is the main by-product of table sugar production. Blackstrap molasses is the remaining by-product of raw sugar production from sugar cane, it is the prevailing type of cane molasses. High test molasses or inverted cane syrup is a by-product of the refineries in which raw sugar is refined into white or table sugar. Both blackstrap and beet molasses are widely used in the fermentation industry. Their approximate composition differs considerably, as indicated in Table 3.151 The data on sugar beet molasses are averages from two (2) samples each of Dutch and Frenchmolasses fromthe 1990 campaign (column A). The US beet molasses data are averages from five (5) factories belonging to American Crystal Sugar over the 1991 season (Column B). The blackstrap molasses data are averages from several samples from Brazil, Dominican Republic and Haiti, over the period 1975-1983. Table 4 is an indication of how complex a medium blackstrap molasses is. Upon diluting to 25%, it was stripped under reduced pressure (40 mm Hg) at 38°C. The distillate was extracted with an ethedpentane (1: 1) mixture. Separation and identification was done with a capillary column and mass spe~trometer.[~] Molasses is produced through nonsugar accumulation during the sugar production process and the accompanying increased solubility of sucrose. Of the non-sugars, the mineral salts have a much greater influence on sucrose solubility than the organic compounds. As a rule of thumb, one gram of mineral salts present in normal molasses will retain five grams of noncrystallizable sucrose. Through chromatographic separation processes, it is possible to recover up to approximately 85 percent of this sucrose
Nutritional Requirements 133 Table 3. Average composition(%)of European(A)and U.S. (B)beet molasses versus Brazilian/Caribbean blackstrap molasses Beet molasses Blackstar Column a Column B water 19.2 18.0 sucrose glucose +fructose 1.0 0.5 27.0 raffinose 1.0 rganic non-sugars 19.0 18.0 ash 11.5 12.1 9.0 Ash components. Sio2 0.1 0.7 K2O 3.9 64 3.5 0.26 Mgc 0.16 0.12 PrOs 0.06 0.03 0.2 1.3 Fe,O 0.02 0.07 Sulfates as SO3 0.55 0.74 1.8 CI l1.5 9.0 Thiamine(B, 1.3 0.01 8.3 Riboflavin(B2) Nicotinic acid 510 8.0 21.0 Ca-pantothenate(B3) 1.3 21.4 Folic acid 2.1 0.025 Pyridoxine-HCl(B2) 5.4 65 Biotin 0.05 1.2 The average viscosity of sample B was 1,062 cP at 45C
Nutrition a1 Requirements I33 Table 3. Averagecomposition(%)ofEuropean (A) andU.S. (B) beet molasses versus BrazilidCaribbean blackstrap molasses Component Beet Molasses Blackstrap Column A Column B water 16.5 19.2 18.0 sucrose 51.0 48.9 32.0 glucose + fructose 1 .O 0.5 27.0 raffinose 1 .o 1.3 organic non-sugars 19.0 18.0 14.0 ash 11.5 12.1 9.0 - Ash components: Si02 CaO K2O MgO p205 Na,,O J33203 co3 A1203 Sulfates as SO, c1 0.1 3.9 0.26 0.16 0.06 1.3 0.02 0.07 3.5 0.55 - 1.6 11.5 - 6.4 0.21 0.12 0.03 1.6 0.03 - - 0.74 0.8 0.7 3.5 1.9 0.1 0.2 0.4 - 1.8 - 0.4 9.0 Vitamins (md 100 2): Thiamine (B,) 1.3 0.01 8.3 Riboflavin (B,) 0.4 1.1 2.5 Nicotinic acid 51.0 8.0 21.0 Ca-pantothenate (B,) 1.3 0.7 21.4 Folic acid 2.1 0.025 0.04 6.5 Biotin 0.05 - 1.2 Pyridoxine-HC1 (B,) 5.4 - The average viscosity of sample B was 1,062 CP at 45°C
13 Fermentation and Biochemical Engineering Handbook Table 4. Isolation Of Some Volatile Compounds In Blackstrap Molasses[5] acetic acid methylformate propionic acid 2-methyl-furamidon-3 isobutyric acid furfurylacetate n-butyric acid methylfurfural isovaleric acid 2-acetylfuran n-valeric acid isocaproic acid guanaco n-caproic acid benzaldehyde 2.5-dimethylpyrazine(1, 4) aspartic acid 2, 6-dimethylpyrazine(1, 4) glutamic acid 2-methyl-6-ethylpyrazine(1, 4) 2-methyl-5-ethylpyrazine(l, 4) Isoleucine trimethylpyrazine (, 4 methionine vanillic acid asparagine p-hydroxy benzoic acid utamine p-coumaric acid(trans-) p-coumaric acid(cis-) p-hydroxphenylacetic acid The composition of molasses varies from year to year, since it depends on many factors, such as variety of sugar cane or beet, soil type, climatic conditions(rainfall, sunshine), time of harvesting, process conditions, et Beet molasses contains approximately 1. 9%N of which roughly consists of betaine. 0.6% amine-n and 0.025% ammoniacal-N molasses does not contain betaine and has less than 50% of the organic nitrogen content of beet molasses. Beet molasses contains a relatively high amount of protein, while cane molasses contains high levels of gums and pectins. Also present are: hemicellulose, reversible and irreversible colloids pigments, inositol, etc. Both types of molasses also contain trace elements vitamins and growth factors, however, cane molasses usually contains more than beet molasses. Beet molasses has a characteristic, often unpleasant smell, and a pH around 8.0; while blackstrap molasses usually has a frui pleasant, mildly acidic smell and a ph value below 7.0
134 Fermentation and Biochemical Engineering Handbook Table 4. Isolation Of Some Volatile Compounds In Blackstrap Molasses[5] methanol methyl formate 2-methyl-furamidon-3 fu firylacetate methylfufiral 2-acetylfuran phenol quaiacol benzaldehyde 2.5 dmethylpyrazine ( 1 , 4) 2,6dimethylpyrazine (1,4) 2-methyl-6-ethylpyrazine (1,4) 2-methyl-5-ethylpyrazine (1,4) trimethylpyrazine (1, 4) syringic acid vanillic acid p-hydroxy benzoic acid p-coumaric acid (trans-) p-coumaric acid (cis-) p-hydroxphenylacetic acid ~~ acetic acid propionic acid isobutync acid n-butyric acid isovaleric acid n-valeric acid isocaproic acid n-caproic acid alanine aspartic acid glutamic acid leucine isoleucine glycine methionine asparagine glutamine valine tyrosine The composition of molasses varies from year to year, since it depends on many factors, such as variety of sugar cane or beet, soil type, climatic conditions (rainfall, sunshine), time of harvesting, process conditions, etc. Beet molasses contains approximately 1.9% N of which roughly 1.2% consists of betaine, 0.6% amine-N and 0.025% ammoniacal-N. Cane molasses does not contain betaine and has less than 50% of the organic nitrogen content of beet molasses. Beet molasses contains a relatively high amount of protein, while cane molasses contains high levels of gums and pectins. Also present are: hemicellulose, reversible and irreversible colloids, pigments, inositol, etc. Both types of molasses also contain trace elements, vitamins and growth factors, however, cane molasses usually contains more than beet molasses. Beet molasses has a characteristic, often unpleasant smell, and a pH around 8.0; while blackstrap molasses usually has a fruity, pleasant, mildly acidic smell and a pH value below 7.0