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ItemDevelopment of corn silk as a biocarrier for Zymomonas mobilis biofilms in ethanol production from rice straw( 2016) Tatsaporn Todhanakasem ; Rashmi Tiwari ; Pornthap ThanonkeoZ. mobilis cell immobilization has been proposed as an effective means of improving ethanol production. In this work, polystyrene and corn silk were used as biofilm developmental matrices for Z. mobilis ethanol production with rice straw hydrolysate as a substrate. Rice straw was hydrolyzed by dilute sulfuric acid (H2SO4) and enzymatic hydrolysis. The final hydrolysate contained furfural (271.95 ± 76.30 ppm), 5-hydroxymethyl furfural (0.07 ± 0.00 ppm), vanillin (1.81 ± 0.00 ppm), syringaldehyde (5.07 ± 0.83 ppm), 4- hydroxybenzaldehyde (4-HB) (2.39 ± 1.20 ppm) and acetic acid (0.26 ± 0.08%). Bacterial attachment or biofilm formation of Z. mobilis strain TISTR 551 on polystyrene and delignified corn silk carrier provided significant ethanol yields. Results showed up to 0.40 ± 0.15 g ethanol produced/g glucose consumed when Z. mobilis was immobilized on a polystyrene carrier and 0.51 ± 0.13 g ethanol produced/ g glucose consumed when immobilized on delignified corn silk carrier under batch fermentation by Z. mobilis TISTR 551 biofilm. The higher ethanol yield from immobilized, rather than free living, Z. mobilis could possibly be explained by a higher cell density, better control of anaerobic conditions and higher toxic tolerance of Z. mobilis biofilms over free cells.
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ItemFermentation of rice bran hydrolysate to ethanol using Zymomonas mobilis biofilm immobilization on DEAE-celluloseBackground: The major challenges associated with the fermentation of lignocellulosic hydrolysates are the reduction in the operating cost and minimizing the complexity of the process. Zymomonas mobilis biofilm has been emerged to resolve these complexities. Biofilm has been reported to tolerate to the toxic inhibitors and easily manipulated toward the cell recycle through the cell immobilization. Results: Z.mobilisZM4 and TISTR 551were able to develop biofilms onDEAE cellulose under the differences in the morphologies. Z. mobilis ZM4 developed homogeneous biofilm that brought DEAE fiber to be crosslinking, while Z. mobilis TISTR 551 developed heterogeneous biofilm in which crosslinking was not observed. Ethanol production under batch and repeated batch fermentation of rice bran hydrolysate containing toxic inhibitors were compared between these two biofilms. TISTR 551 biofilm produced the maximum yield (YP/S) of 0.43 ± 0.09 g ethanol/g glucose (83.89% theoretical yield). However the repeated batch could not be proceeded due to the bacterial detachment. Z. mobilis ZM4 biofilm produced the maximum yield (YP/S) of 0.177 ± 0.05 g ethanol/g glucose (34.74% theoretical yield) in the batch culture and the biofilm remained intact to proceed along the repeated batch. The highest ethanol yield (YP/S) in the repeated batch of Z. mobilis ZM4 was 0.354 ± 0.07 g ethanol/g glucose (69.51% theoretical yield). Conclusions: Homogeneous biofilm structure of Z. mobilis provided more recycle beneficial over the heterogeneous biofilm structure for the ethanol production from lignocellulosic hydrolysate.
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ItemMicrobial Biofilm in the industry( 2013) Tatsaporn TodhanakasemBiofilms represent negative and positive attributes in the industries. Biofilm is a functional consortium of microorganisms attached to either biotic or abiotic surfaces and embedded under the extracellular polymeric substances (EPS). Spoilage and pathogenic microorganisms can develop biofilms on food industrial surfaces that can lead to food spoilage and disease transmission when the inappropriate clean up and control have been applied in the food industies. However, single and mixed species of microbial biofilms also represent tremendous advantages in bioprocesses and waste treatments. Biofilm reactors have been employed in order to improve the productivities, stability of the processes and reduce the production cost. To understand biofilm, numerous direct and indirect experimental approaches have been used to study the biofilms. Molecular genetics approaches have led to study on the process of biofilm development in order to understand its genetic regulations.
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ItemZymomonas mobilis biofilm formation on different types of carriers( 2016) Tatsaporn Todhanakasem ; Rashmi TiwariZymomonas mobilis biofilm have been proposed to enhance the bioethanol production from agricultural derived materials. Z. mobilis biofilm reactor has been prospected to be used for a large scale bioethanol production. The cost effective carrier for Z. mobilis biofilm reactor was searched. This study investigated the biofilm forming abilities of Z. mobilisstrain TISTR 551 and ZM4 on biotic (loofah and corn silk) or abiotic carriers (flatted sheet polyvinyl chloride, PVC). Biofilm formation was visualized for 3 consecutive days under the bright-field microscope. Only Z. mobilis TISTR551 represented the biofilm forming ability on corn silk under the microscopic observation, while no biofilm formation on loofah and PVC was observed. The mature biofilm was developed on day 3. The biofilm formation was also quantitatively analyzed based on the weight differentiation of the carrier and the carrier with the bacterial attachment. The net biomass weight of TISTR 551 and ZM4 on corn silk carrier was 0.6 ±0.1 g and 0.33± 0.1g respectively. Therefore, corn silk illustrates its potential to be used as a cost effective biocarrier for Z. mobilis biofilm.