Production, characterization and applications of raw starch degrading enzyme by thermophilic filamentous bacterium laceyella sacchari LP175

Name: Thanasak Lomthong

LCSH: Kasetsart University -- Dissertations. Ph.D. (Microbiology) 2017

Classification :.LCCS: QR82.T4

LCSH: Kasetsart University. Department of Microbiology -- Dissertations

LCSH: Thermoactinomycetaceae

LCSH: Thermophilic bacteria

LCSH: Enzymes

LCSH: Amylases

Abstract: High efficiency of raw starch degrading enzyme (RSDE) produced by a newly isolated thermophilic filamentous bacterium, Laceyella sacchari LP175. Medium composition and physical factors that enhanced the production of RSDE were optimized using Plackett–Burman design and central composite design which showed an optimized concentration at 4.93 g/L and 2.8 g/L of raw cassava starch and yeast extract, respectively at a pH of 6.5, a temperature of 45 oC and an aeration rate of 0.5 vvm in a 3 L airlift fermenter. This yielded 278 U/mL, at 36 h cultivation, an increase in enzyme production and productivity of 154 and 220 folds, respectively as compared with un-optimized condition. RSDE produced by L. sacchari LP175 with commercial glucoamylase synergistically enhanced the hydrolysis of 300 g/L dried cassava chips (71% starch content) to 157 g/L reducing sugars, equivalent to 66.3% hydrolysis at pH 6.5 and 50 oC for 12 h. The comparative study on bioethanol production in a non-sterile system from dried cassava chip by 3 different processes were investigated; the maximum production, 90.9 g/L (88% theoretical yield). RSDE was purified with a 14.7 purification folds and 40.5% yield. The purified enzyme has a molecular weight of 50.4 kDa, and showed an optimum pH and temperature at 6.5 and 50 oC, respectively. The N-terminal amino acid sequence showed a 100% homology with α amylase from Laceyella sp. DS3 and Thermoactinomyces vulgaris. The major end product of the raw cassava starch hydrolysis by purified enzyme was maltose (85%). This suggests that RSDE from L. sacchari LP175 was an α-amylase. Bioinformatic analysis indicated that the RSDE gene contained 1362 bp encoding 453 amino acids which cloned and expressed in E.coli for production of RSDE and understanding of its structure-function for further development and engineering. The co-production of poly (L-lactide) (PLLA)- degrading enzyme and RSDE by L. sacchari LP175 using low-cost agricultural crops as substrates was acheived. The crude enzymes degraded bioplastic PLLA/thermoplastic starch (TPS) (50:50) blend film up to 99.7% within 4 h at an initial pH of 9.0 which could be applied to reduce the global environment from non-biodegradable materials.

Kasetsart University. Office of the University Library

Address: Bangkok

Email: tdckulib@ku.ac.th

Name: Vichien Kitpreechavanich

Role: Thesis Advisor

Name: Sunee Chotineeranat

Role: Thesis Co-Advisor

Name: Alain Marty

Role: Thesis Co-Advisor

Created: 2017

Modified: 2023-06-29

Issued: 2023-06-29

วิทยานิพนธ์/Thesis

application/pdf

URL: https://kasetsart.idm.oclc.org/login?url=https://www.lib.ku.ac.th/KUthesis/2560/thanasak-lom-all.pdf

CallNumber: QR82.T4.T43

eng

DegreeName: Master of Science

Level: Doctoral Degree

Descipline: Microbiology

Grantor: Kasetsart University

©copyrights Kasetsart University

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