Effect of Incubation Temperature on Growth of Acetobacter xylinum 0416 and Bacterial Cellulose Production

The objective of this research was to investigate the effect of incubation temperature towards the growth of Acetobacter xylinum 0416 and the production of bacterial cellulose. Fermentation of A.xylinum 0416 were carried out for 5 days in static condition using Hestrin & Schramm (HS) medium with initial glucose concentration of 4.0% (w/v) and initial pH of 6.4. The incubation temperature were varied at 5°C, 20°C, 25°C, 27°C, 28°C, 30°C, 35°C and 40°C respectively. Results indicated that 28°C served as the best incubation temperature for the growth of A.xylinum 0416 and produced the highest amount of bacterial cellulose with total dried weight of 0.3722 g/l. Meanwhile at incubation temperature of 5°C and 40°C, no significant growth of A.xylinum 0416 and bacterial cellulose were obtained. As a conclusion, incubation temperature plays an important role for the growth of A.xylinum 0416. The best incubation temperature is at 28°C in which the sufficient energy will be provided for bacterial growth thus enhancing the cellulose biosynthetic pathway in order to convert glucose into bacterial cellulose.

Microbial degradation of cellulosic material under intermediate-level waste simulated conditions

Under the alkaline conditions expected in an intermediate-level waste repository, cellulosic material will undergo chemical hydrolysis. This will produce hydrolysis products, some of which can form soluble complexes with some radionuclides. Analyses of samples containing autoclaved tissue and cotton wool incubated in a saturated solution of Ca(OH)2 ( pH > 12) confirmed previous reports that isosaccharinic acid (ISA) is produced from these cellulose polymers at high pH. However, when inoculated with a sediment sample from a hyperalkaline site contaminated with lime-kiln waste, microbial activity was implicated in the enzymatic hydrolysis of cellulose and the subsequent production of acetate. This in turn led to acidification of the microcosms and a marked decrease in ISA production from the abiotic alkali hydrolysis of cellulose. DNA analyses of microbial communities present in the microcosms further support the hypothesis that bacterial activities can have a controlling influence on the formation of organic acids, including ISA, via an interplay between direct and indirect mechanisms. These and previous results imply that microorganisms could have a role in attenuating the mobility of some radionuclides in and around a geological disposal facility, via either the direct biodegradation of ISA or by catalysing cellulose fermentation and therefore preventing the formation of ISA.

Study on the Fermentation of Fuel Ethanol from Corn Stover Pretreated by Propionic Acid

Simultaneous saccharification and fermertation (SSF) were studied to produce ethanol from corn stover, which include three continuous stages, stover pretreatment, cellulose fermentation, and ethanol production. Firstly, the crude was treated by propionic acid, and the disposal rate of lignin and hemicellulose in corn stover was 60.6%, 98.5%, respectively, with a residual rate of cellulose 90.68%. Then, cellulase production was carried out byTrichoderma reeseiRut C-30. 10% stillage and other nutrition were added to the pretreated corn stover, water moisture and initial pH were adjusted to 70% and 4.8, liquid inoculum was (1.7~2.0)×107spore/g stover. The stover was kept under 30°C for 7d, then mixed with equal pretreated stover. Ratio of water was 2, the inoculum was 3.2×107cell (Saccharomyces cerevisiae)/g substrate, After incubated at 36°C for 72h, the SSF process achieved a yield of ethanol (0.326g/g substrate).