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Prparation of Bacterial Cellulose with Jerusalem Artichoke

Author: HanZuo
Tutor: CaoZhangJun；HongFeng
School: Donghua University
Course: Biochemical Engineering
Keywords: Jerusalem artichoke inulin acid hydrolysis enzymatic hydrolysis bacterial cellulose
CLC: TQ352.1
Type: Master's thesis
Year: 2012
Downloads: 74
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Abstract

Bacterial cellulose (BC) is a natural nano-structured material produced by microorganisms. Compared with the plant cellulose, it has high crystallinity, excellent biocompatibility, strong water imbibition and good mechanical strength. Therefore, BC has a wide range of applications for food, papermaking, and textile industry and biomedicine area. But the high cost and low yield become a bottleneck of large-scale industrial production. The main research directions by means of traditional approaches are to screen an excellent strain and optimize fermentation technical conditions. However, the traditional approach is labour-intensive and low efficiency. For large-scale production of BC, exploitation of a cost-effective carbon source is one of the new methods.It is reported that fructose can be utilized by Gluconacetobacter xylinus to produce BC, which has the advantage of high output and the disadvantage of expensive price. Inulin is the main content in tubers of Jerusalem artichoke and is composed of fructosan. This fructosan is a polysaccharide of D-furan fructose viaβ-2,1 glycosidic bond. Based on this molecular structure, hydrolysis can generate large amount of fructose and little glucose for BC production. Compared with lignocellulose feedstock, Jerusalem artichoke has features of high output, easy survival and low cost for mass production. In this paper, the single factor and orthogonal experiments were designed to optimize conditions of inulin extraction, acidolysis and enzymolysis by using fresh Jerusalem artichoke tuber as raw material. Hydrolyzates were applied to ferment more bacterial cellulose. The yields, mechanical property and SEM of BC producted by different carbon sources were compared and analyzed.This experiment analyzed components and water extraction of fresh Jerusalem artichoke tuber. The tuber was steamed to denature inside enzymes, then juiced with water and placed in hot water to extract. The optimal conditions were that total sugar contents of 32.8 g/L could be reached at 90℃for 2 h with solid-liquid ratio of 1:10.Jerusalem artichoke tuber and inulin were hydrolysised by H2SO4 and by enzymes in order that the materials would be degraded into fructose and glucose, which would be used by G. xylinus. For acid hydrolysis, the single-factor experiements were firstly performed. And then based on the results of single-factor experiments, ortogonality measure was used to optimize the hydrolytic conditions.For inulin, the optimal conditions were 105℃for 30 min with 0.5 mol/L H2SO4 and solid-liquid ratio of 1:10, and hydrolysis of sugar reached 98.3%. For Jerusalem artichoke, the optimal conditions were that hydrolysis sugar yield of 65.2% could be reached at75℃for 40 min with 0.6 mol/L H2SO4 and solid-liquid ratio of 1:25. Finally the acid hydrolysates were analyzed by TLC and HPLC, and the main components of the acid hydrolyzates were found to be glucose in inulin and fructose in Jerusalem artichoke, respectively.Finally, the acid hydrolysis and enzymatic hydrolysis of both Jerusalem artichoke and inulin were used for preparation of bacterial cellulose. The yields, mechanical properties and SEM of BC producted by different carbon sources were compared and analyzed. Experimental results showed that different hydrolyzates could produce BC. Compared to conventional carbon sources, cultures with the hydrolysate of Jerusalem artichoke achieved the highest yield of 41.3 g/L, followed by the enzymatic hydrolysate of inulin (39.2 g/L). BC from the acid hydrolyzate of Jerusalem artichoke had the biggest Young’s modulus (9.31 Mpa).

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