Maltotetraose production using Pseudomonas stutzeri exo-alpha-amylase in a membrane recycle bioreactor
Woo, Gun-Jo
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Permalink
https://hdl.handle.net/2142/21352
Description
Title
Maltotetraose production using Pseudomonas stutzeri exo-alpha-amylase in a membrane recycle bioreactor
Author(s)
Woo, Gun-Jo
Issue Date
1991
Doctoral Committee Chair(s)
Witter, Lloyd D.
Department of Study
Food Science and Human Nutrition
Discipline
Food Science
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Agriculture, Food Science and Technology
Biology, Microbiology
Engineering, Chemical
Language
eng
Abstract
To develop a continuous process for the production of maltotetraose (G$\sb4$), a concept of enzymatic modification of biopolymers, separation of products from the reaction mixture, and the re-use of the soluble enzyme has been employed. Application of this concept to a starch-maltotetraohydrolase system to produce maltotetraose has been demonstrated in a membrane recycle bioreactor (MRB). The enzyme was partially purified to a specific activity of 21.5 units/mg protein for use in the reactor system. The effects of four operational variables--concentration of the enzyme, substrate concentration, flux, and reactant volume--on the product concentration, G$\sb4$ production rate, and the relative product purity were examined. The productivity at a steady state under optimized conditions was 0.99-1.11 g/L/hr depending on the kinds of starches. For the steady state conditions, a best fit model for prediction of yield was statistically developed using stepwise regression based on the data obtained from the optimization study. The productivity was also compared using five kinds of starches differing in the ratio of amylose to amylopectin, the amylopectin chain lengths, and the level of starch modification. Considering all the criteria of product purity, total product output, and production rate except fouling, unmodified native corn starches were shown to be better substrates than soluble starch. The estimated total amount of fouling in the membrane, calculated from the mass balance equation, was 69 mg Glucose equivalent during 6 hr reaction when running 0.25% soluble starch. This mass balance equation also indicated that the $\alpha$-limit dextrin was accumulated in the reactor due to the exo-mechanism of the enzyme. One long-term operation of the MRB was performed to determine the steady state stability and the product purity at prolonged reaction times. A product purity over 50% was maintained until 13 hr reaction time. The relative percent of maltotetraose in the permeate after 13 hr decreased to 44% when soluble starch was used as substrate. This level of product purity can be used for the manufacture of G$\sb4$ syrup containing 50% maltotetraose, which has many applications in the food and sugar industry. The relatively short-term operation of the MRB system was shown to be appropriate for high purity (83-84%) maltotetraose production for biochemical, clinical, and pharmaceutical applications.
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