| Summary: | 碩士 === 東海大學 === 食品科學系 === 93 === ABSTRACT
To solve the problem of environmental contamination caused by Shochu thin stillage, this research applied a fermentative production of bacterial cellulose using Acetobacter xylinum as the starter and disposed Shochu thin stillage as the fermenting substrate. The object of this research is to solve the waste-product problem of Shochu factory and to lower the production cost of bacterial cellulose.
Acetobacter xylinum A-7 isolated from Kombucha was selected as the starter organism. Activation of this starter by static incubation (30℃/2-4days) showed good activity and stability.
Regarding the treatment and composition of the substrate, studies showed that a higher cellulose yield was obtained from a 1：1（v/v） diluted and 90℃/15 min heated thin stillage substrate containing 1％（v/v）ethanol , 1％（v/v）acetic acid , 0.32％（w/v）yeast extract , 0.17％（w/v）peptone and a initial substrate pH of 3.6. The concentration of added yeast extract and initial substrate pH were statistically estimated by the Response Surface Methodology（RSM）. Besides, incubation temperature of 30℃and S/V=0.47cm-1could increase the cellulose yield.
Results on the simulated mass-production（room temperature/15 days）of cellulose from shallow plate（375 cm2 surface area） indicated that good cellulose yield could be achieved in a 1：1（v/v）diluted and 80℃/5 min heated Shochu thin stillage substrate containing 1％（v/v）ethanol 1％（v/v）, acetic acid , 0.26％（w/v）yeast extract and 0.16％（w/v）peptone. Considering covering materials of the shallow plates , polyethylene membrane with piercing holes provided good ventilation and avoided surface holes on cellulose pellicle caused by vapor drops.The two-stage（stirring/static）incubation method neither saves time nor leads to a higher cellulose yield as compared with the traditional static incubation method . Cellulose pellicle with better colorimetric values could be obtained at 30℃incubation temperature.Soaking in solutions containing acetic acid（1％, v/v）or sucrose（0~30ºBrix）reduced the hardness, gumminess and chewiness of cellulose pellicle. Hardness of washed and heated (100 ℃/15) cellulose-pellicle fall off significantly, while the springiness , cohesiveness, gumminess and chewiness incerased singinificatly.The freeze-dried（-60℃/80 millitorr/24 h）cellulose-pellicle had higher rehydration ratio（79％）than hot-air dried(40℃＆70℃ /24h)method cellulose-pellicle（5％-9％). Cellulose pellicle produced from this study（two-stage incubation）had higher sensory acceptability than those imported from Hainan and Vietnam. Soaking solution with 0.5％（v/v）acetic acid showed best antimicrobial effect during a 30-day storage of cellulose -pellicle at room temperature.
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