BIOLOGICAL AND BIOCHEMICAL CHARACTERIZATION OF Leuconostoc mesenteroides ISOLATES AND THEIR BIO-DEGRADATION LEVELS OF SELECTED POST HARVESTED SUGARCANE (Saccharum officinarum) VARIETIES IN WESTERN KENYA

Abstract

Sugarcane (Saccharum officinarum) is a highly perishable crop that must be processed promptly after harvesting. In many countries that cultivate sugarcane, such as Kenya, there is typically a delay of three to seven days before milling occurs in sugar factories. This lag time results in the degradation of the sugar due to the action of the Leuconostoc mesenteroides bacterium. This bacterium converts sucrose into glucose and fructose, which cannot be crystallized, while also producing dextran, a branched glucose polymer. The presence of dextran in the sugar juice leads to specific problems, particularly in the crystallization process. The biodegradation of sugar in harvested sugarcane varies by variety. In Kenya, numerous sugarcane varieties are available to farmers, but the extent of their deterioration remains unclear. The use of sodium chloride in controlling sucrose deterioration in harvested sugarcane has been reported. However, the effective sodium chloride concentration for this purpose is not yet known. This study, therefore, sought to characterize three isolates of Leuconostoc mesenteroides, profile the biodegradation levels of selected post-harvested sugarcane, and determine a suitable concentration of sodium chloride for controlling the deterioration of harvested sugarcane. The three Leuconostoc mesenteroides isolates were collected from Kakamega, Nyando, and Sony sugar and sent to the Sugar Research Institute in Kisumu for isolation and identification on selective media. The confirmation test for the isolates was conducted by metabolizing different sugars. Four commonly adopted varieties, KEN 83-737, KEN 82-808, N14, and Co 421, were used to profile the deterioration levels by aseptically inoculating them with the three isolates in a closed bucket. Changes in deterioration parameters, namely Brix% juice, pol% juice, dextran, and pH, were measured over 10 days to facilitate evaluation. The results indicate that the Sony sugar isolate showed the highest levels of sugarcane deterioration, producing 1654.99 ppm of dextran. In contrast, the Kakamega and Nyando sugar isolates exhibited the least deterioration of sugarcane, producing 820.95 and 820.39 ppm of dextran, respectively. N14 and Co421 were the most and least degraded sugarcane varieties, losing 4.84 and 2.41 pounds of sucrose to dextran, respectively. Finally, Co421 and KEN83-737 varieties were specifically selected and used to determine the suitable sodium chloride concentration for controlling staleness in harvested sugarcane. The two varieties were treated with 6.5% NaCl, 13.0% NaCl, and a zero control supplemented with covering. Deterioration parameters were collected to evaluate sucrose loss. The results indicate that when harvested sugarcane is treated with 6.5% NaCl and 13.0% NaCl, sucrose loss is reduced by 18.04% and 18.31%, respectively. This study recommends prioritizing varieties susceptible to deterioration for milling to avoid sucrose loss. It also suggests that sugarcane milling after harvesting should be managed based on the region of harvest.