Enzymic Hydrolysis of Raffinose for the Improvement of Sugar Recovery in Beet Processing

Abstract

Enzyme Alpha- galactoside that finds potential use in the hydrolysis of raffinose in the beet sugar manufacture, was produced by locally isolated cultures of both Bacillus species and mould Mortierella species by submerged fermentation. Bacillus stearothermophilus PCSTR-16, among bacterial cultures, synthesized maximum amount of enzyme and its nutritional studies were further carried out. Alpha-galactosidase formation, in general, was maximum 10-18 hrs, after inoculation. The agriculture produce, containing alpha galactoside sugars, such as mung (Phaceolus mungo), mash (Phaceolus-radiatus), peanut meal, cotton seed cake, rape seed cake of soybean meal were evaluated for enzyme production. The enzyme formation, however, was maximum in the presence of soybean meal and mung i.e. 97 and 90 units/l respectively. Melibiose or raffinose, alpha galactoside sugars, was found to be the best inducer of enzyme production. The addition of casein, casein hydrolysete, peptone or tryptone increased cell synthesis and enzyme formation was lesser as compared with soybean meal. The enzyme formation in mycelial pellets of Mortierella vinacea var raffinose utilize was also studied in shake flasks. The mycelia pellets are easier in handling than soluble enzyme. Of all carbon sources such as fructose, glucose, galactose, raffinose, lactose or maltose, the alpha galactosidase synthesis, both intracellular and extracellular, was maximum in the presence of lactose or raffinose. Effect of nitrogen sources on mycelial dry weight and enzyme production was also studied. The mycelial formation was maximum in the presence of sulphite waste liquor or peptone and it was greatly affected in the presence of casein, casein hydrolysate, tryptone or inorganic nitrogen sources. The enzymic activity however, was maximum in the control cultures containing corn steep licour. Alpha-galactoside production was investigated by solid substrate fermentation using wheat bran, rape seed meal, soybean meal or defatted rice bran in litre conical flasks. The enzyme formation was maximum in the presence of soybean meal and it decreased in the order of wheat bean or rape seed meal but invertase, an undesirable enzyme in this fermentation, was also formed. The mycelial pellets were used to study the rate of hydrolysis of raffinose in beet molasses. More than 60% of raffinose was hydrolysed. The use of mycelial pellets during beet sugar processing, however, is to be studied.