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The continuous production of 1,3-propanediol (1,3-PDO) was investigated with Clostridium beijerinckii NRRL B-593 using raw glycerol without purification obtained from a biodiesel production process. Ceramic rings and pumice stones were used for cell immobilization in a packed-bed bioreactor. For comparison purpose, a control bioreactor with suspended culture was also run. The effect of hydraulic retention time (HRT) on the production of 1,3-PDO in both immobilized and suspended bioreactors were also investigated. The study revealed that HRT is an important factor for both immobilized and suspended systems and a HRT of 2 h is the best one in terms of volumetric production rate (g 1,3-PDO/L/h). Furthermore, cell immobilization had also obvious benefits especially for the robustness and the reliability of the production. The results indicated that cell immobilization achieved a 2.5-fold higher productivity in comparison to suspended cell system. Based on our results, continuous production of 1,3-PDO with immobilized cells is an efficient method, and raw glycerol can be utilized without any pretreatment.

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Owing to rising population and increasing energy demand, renewable energy resources become the most convenient and promising solution. Hence, solar power plant investments and photovoltaic module numbers have risen sharply. Turkey is one of the tight followers of the energy trends, thanks to its rising energy demand and economic power. However, the consequences of the massive plant wastes importance in term of economically and environmentally have not been understood yet. Almost 70% of the modules are formed by glass and the rest accumulates economically valuable metal materials, which are silver, aluminium and copper. These three main materials are substantially important in the overall waste. Not only the economic value, but also the environmental impacts of the mining effluents to excavate these metals are causing emission problems. As a chain reaction, the higher energy demand triggers a search for new and renewable energy resources. This is why popularity of solar energy has increased. Solar energy can be absorbed and transformed through photovoltaic modules, which contain glass and three main metals. In order to respond for the production of modules, metals are fundamental. This need triggers the need of metals mining excavations and emissions. In this respect, in the near future, thanks to the rising investments on photovoltaic modules and the CO2 emissions coming from mining, the wastes of photovoltaic modules and the need of recycling will become more important. That is why, in this study it is aimed to present environmental benefits and economic recoveries of recycling photovoltaic module in Turkey.

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Aims:  The feasibility of the continuous production of a valuable bioplastic raw material, namely 1,3‐propanediol (1,3‐PDO) from biodiesel by‐product glycerol, using immobilized cells was investigated. In addition, the effect of hydraulic retention time (HRT) was also analysed. Methods and Results:  Ceramic balls and ceramic rings were used for the immobilization of a locally isolated strain; Klebsiella pneumoniae (GenBank no. ). HRT of 1 h is the best one in terms of volumetric production rate (g 1,3‐PDO l−1 h−1). The results indicated that ceramic‐based cell immobilization achieved a 2‐fold higher production rate (10 g 1,3‐PDO l−1 h−1) in comparison with suspended cell system (4·9 g 1,3‐PDO l−1 h−1). Conclusions:  Continuous cultures with immobilized cells revealed that 1,3‐PDO production was more effective and more stable than suspended culture systems. Furthermore, cell immobilization had also obvious benefits especially for resistance of the production for extreme conditions (high organic loading rates, cell washouts). The results were important for understanding the significance of continuous immobilization process among other well‐known 1,3‐PDO fermentation processes. Significance and Impact of the Study:  This work is a promising process for further studies, as the immobilized micro‐organism was able to reach high volumetric production rates at short HRT, it has an important role in tolerating and converting glycerol during fermentation. Therefore, HRT is a very significant operational parameter (P value <0·05) directly affecting the bioreactor performance and production rate.

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