Browsing by Subject "Bioproducts/Biosystems Science Engineering and Management"

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    Bio-fuel production by using integrated anaerobic fermentation.
    (2012-01) Xu, Lei
    Saccharification is one of the most critical steps in producing lignocellulose-based bio-ethanol through consolidated bioprocessing (CBP). However, extreme pH and high ethanol concentrations are commonly considered potential inhibitors for the application of Clostridium sp. in CBP. The fermentation of several saccharides derived from lignocellulosics was investigated with a co-culture consisting of Clostridium themocellum and Clostridium thermolacticum with or without immobilization. Alkali environments proved to be more favorable for ethanol production. Fermentation inhibition was observed at high ethanol concentrations (>8g/L) and extreme pH (>10). However, low levels of initial ethanol addition resulted in an unexpected stimulatory impact on the final ethanol productions for all cultures under selected conditions. The co-culture was able to actively ferment glucose, xylose, cellulose and micro-crystallized cellulose (MCC). The ethanol yield observed in the co-culture was higher (up to two-fold) than in mono-cultures, especially in MCC fermentation. The highest ethanol yield (as a percentage of the theoretical maximum) observed were 75% (w/w) for MCC and 90% (w/w) for xylose. Immobilization technique using sodium alginate is efficient in improve the ethanol production during co-culture fermentation, although the immobilization is not able to change the ethanol sensitivity of this co-culture. The ethanol yield through the use of immobilized technique increased to 97% of the theoretical efficiency for glucose. For cellobiose and MCC under optimized condition, the ethanol yields were approaching 85% of the theoretical efficiency. In order to examine the feasibility of this immobilization co-culture on lignocellulosic biomass conversion, untreated and pretreated aspen fermentations were performed. The immobilization co-culture shows clear benefit in bio-ethanol production in CBP process. With a 3h, 9% NaOH pretreatment, the aspen powder fermentation yield approached 78% of the maximum theoretical efficiency, which is almost twice the yield of the untreated aspen fermentation. Keywords: Consolidated bioprocessing, Clostridium sp., Fermentation, Co-culture, Lignocellulosic ethanol, Immobilization, Alginate gel.
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    Biodiesel production from algae through in situ transesterification technology
    (2012-12) Ma, Xiaochen
    Biodiesel, a promising renewable biofuels, is receiving increased attentions. Due to the high price of vegetable oils and the land use competition of biodiesel feedstock production and food production, it is necessary to find other ways to lower the biodiesel production cost and reduce the pressure on food and feed supplies. One possibility to overcome these problems is to produce biodiesel from microalgae feedstock using advanced conversion process. The conventional biodiesel production involves a two-step process in which oil is first extracted from oil feedstock and then subjected to transesterification step. Unfortunately, it is hard to extract oil from algae, making algae based biodiesel production very costly. In this thesis project, an innovative in situ direct transesterification method was investigated. In situ direct transesterification method combines the oil extraction and transesterification process into one step. In this project, microalgae (Chlorella Vulgaris) were used as the feedstock and several factors affecting the final lipid conversion rate were tested and optimized. At room temperature, the best conditions for the in situ transesterification process are: concentration of catalyst (KOH), 2% of the lipid content, reaction time, 10 h, and the methanol amount, 16.4 ml. At temperatures above 45 °C, the optimal reaction time was 4 h. It was found that 60 °C was better than 45 and 75 °C. Almost all the pretreatments tested were able to improve lipid conversion rate. The best pretreatment was the combination of methanol soaking and microwave irradiation, which increased the rate of conversion by 14.8%. The two-step traditional transesterification method was also tested for comparison purpose. The result suggested that in situ direct transesterification produced higher lipid conversion rate than the conventional transesterification process, and could be an alternative, efficient and economical process for algal biodiesel production.