Effect of dextran and enzymatically decomposed dextran on calcium carbonate precipitation

Abstract

The effect of dextran's molecular mass distribution (T40, T500, T2000, and enzymatically decomposed T2000) on the size and shape of calcium carbonate particles precipitated during carbonation, a step in the sugar manufacturing process, was investigated. Image analysis combined with size exclusion chromatography was used to distinguish harmful and harmless dextran sizes aiming at targeted mitigation of dextran‐related effects by dextranase. The data indicate that dextran with molecular masses above 10 kDa promotes agglomeration, indicated by an increase in particle projection area. This effect was especially found for broadly distributed intermediate but rather low molecular mass dextran (10–85 kDa). Based on particle shape data, the agglomeration of calcium carbonate crystals in the absence and in the presence of low molecular mass dextran (<85 kDa) appears to be oriented and similar to each other. In contrast, the data suggest that high molecular mass dextran (>85 kDa) promotes nonoriented agglomeration and an increase in surface roughness. Once the dextran was significantly decomposed by enzyme action (10 or 50 mg/kg juice) to smaller molecules in the size range below 10 kDa, no dextran‐related effects on particle size and shape were found anymore. Practical applications The presence of dextran is known to cause several adverse effects during sugar manufacture. Among them, dextran can affect the size and shape distribution of calcium carbonate particles precipitated during carbonation as a part of the sugar beet raw juice purification. As a result, the purification as well as the filtration process can be affected. These dextran‐related effects are usually mitigated by enzymatic decomposition, a gradual reduction in molecular mass. For a targeted enzyme application, the decomposition products need to be identified and the corresponding effects due to varying molecular mass fractions on the precipitation of calcium carbonate need to be analyzed. Only then, a sufficient decomposition to harmless molecule sizes can be ensured. Thus, the data gathered give a clear guidance for dextranase treatment in sugar manufacture.

Combined enzymatic degradation of dextran and starch towards enhancement of the raw cane sugar juice filtration efficiency

“…Raw cane sugars from various geographical origins (Iran, India and Brazil) were collected and used in analysis. The samples were classified into two groups: domestic (samples 1-9, Iran) and imported (samples 10-12, India; samples [13][14][15][16][17]Brazil). Dextranase (EC 3.2.1.11) and α-amylase (EC 3.2.1.1) enzymes originating from Penicillium sp.…”

“…Starch exists intrinsically in sugarcane plant and passes to raw juice and subsequently to raw sugar (11,12). Dextransucrase and levansucrase enzymes derived by Leuconostoc mesenteroides throughout sucrose hydrolysis and glucose polymerization catalyse the dextran generation which represents an undesirable compound in sugarcane juices and syrups due to sucrose loss (13). Moreover, dextran and starch may be incorporated onto sugar crystals surface by adsorption and/or into sugar crystals via co-crystallization (14).…”

“…Furthermore, enzymatic procedure was successfully utilized for individual hydrolysis of dextran and starch in sugarcane juice (17,18,19). Bhatia et al (2016) applied enzyme dextranase for dextran degradation in raw sugarcane juice to improve quality of sugarcane juice (17) while Abraham et al (2019) used enzymatic degradation to study the effect of dextran's molecular mass on size and shape distribution of calcium carbonate particles precipitated during carbonation on synthetic thin juice of 15% (m/m) refined sucrose (13). Alpha-amylases have been used as sugarcane processing aids to solve viscosity and raw sugar filtration problems that arise from starch (18).…”