外文翻譯--從廚余垃圾發(fā)酵中分離和收集有機酸的綜合過程(英文）

1、African Journal of Biotechnology Vol. 8 (21), pp. 5807-5813, 2 November, 2009 Available online at http://www.academicjournals.org/AJB ISSN 1684–5315 © 2009 Academic Journals Full Length Research Paper Separat

2、ion and recovery of organic acids from fermented kitchen waste by an integrated process Farah Nadia Omar, Nor’Aini Abdul Rahman*, Halimatun Saadiah Hafid, Phang Lai Yee and Mohd Ali Hassan Department of Bioprocess Tech

3、nology, Faculty of Biotechnology and Biomolecular Sciences, University Putra Malaysia, 43400 Serdang, Selangor, Malaysia. Accepted 4 September, 2009 Organic acids produced from anaerobic digestion of kitchen waste were

4、recovered using a new integrated method which consisted of freezing and thawing, centrifugation, filtration and evaporation. The main organic acid produced was lactic acid (98%). After the freezing and thawing process,

5、 73% of the total suspended solids were removed and the organic acids were elevated from 59.0 to 70 g/L. The evaporation technique was used to further concentrate the organic acids up to 224 g/L. Using the integrated

6、recovery method, the reduction of the total suspended solids in the solution achieved was about 93%. The material balance for the recovery process was also presented. Key words: Anaerobic digestion, kitchen waste, orga

7、nic acids, recovery. INTRODUCTION The remarkable growth economy in Malaysia has brought tremendous population growth which then resulted in a huge amount of municipal solid waste (MSW) being generated throughout the y

8、ear. MSW is usually dumped in landfills and degraded into simpler compounds. How- ever, due to the scarcity of land and the constraint of landfill areas, alternative methods should be considered in order to reduce the

9、 space needed for landfills. Incineration is also an option (Ohkouchi and Inoue, 2006) as it is an easy final disposal method but large amounts of energy will be wasted in the burning process (Tsai, 2008). Since 22-5

10、4% of MSW consists of food and organic wastes (Kathirvale et al., 2003), bioconversion of MSW into useful products is feasible and its treatment cost can be reduced too. Food waste contains about 80% of moisture whi

11、ch is easily biodegradable and is rich in nutrients and micro- flora (Wang et al., 2001). Due to these characteristics, biological treatments are preferred. One of the most practical biological treatments is anaerobic

12、 digestion. It is a great tool to stabilize a large volume of waste materials economically and effectively (Sakai et al., 2000). It also *Corresponding author. E-mail: nor_aini@biotech.upm.edu.my. Tel.: 603 8946

13、6669. Fax: 603 8946 7510. produces low biomass and is able to destroy pathogens (Banarjee et al., 1999). Food waste could be anaero- bically fermented to produce volatile fatty acids, alde- hydes, alcohols and carbon d

14、ioxide (Stabnikova et al., 2006). Rather than being degraded and unexploited in the landfills, food waste can be utilized for many applications such as the production of bioplastics (Sakai et al., 2004), biogas (Zhu

15、et al., 2008), biohydrogen and ethanol productions (Kim et al., 2004), composting (Tsai, 2008; Adhikari et al., 2008) and organic acids production (Ohkouchi and Inoue, 2007; Zhang et al., 2008). Organic acids are or

16、ganic compounds which have been extensively used in the food and beverages indus- tries, pharmaceutical industries, cosmetics, and deter- gents and recently they are extensively used for bio- polymer production (Sauer e

17、t al., 2008). There are two ways to produce organic acids which are chemical synthesis or biological synthesis (Altaf et al., 2007). Whether it is chemically or biologically synthesized, the critical stage of the pro

18、cess is product recovery. Down- stream processes including separation, extraction and purification of organic acids which contribute more than 60% of the overall production cost (Han et al., 2000). Several methods hav

19、e been reported for extracting organic acids from the fermentation broth such as electrodialysis (Huang et al., 2007), membrane filtration (Kang and Chang, 2005), solvent extraction (Harington Omar et al.

20、 5809 Figure 2. Organic acids profile in 50 L bioreactor. Total organic acids (-?-), lactic acid (-?-), acetic acid (-?-) and formic acid (-?-). Results are means for duplicate experiments. Figure 3. Profile of pH (-?-

21、) and bacteria distribution (-?-) during kitchen waste fermentation. Results are means for duplicate experiments. shown). After seven days of fermentation, total sus- pended solids were reduced at 62%. Organic acids r

22、ecovery and total suspended solids reduction Figure 4 shows the organic acids, total suspended solids and Total Kjeldahl Nitrogen obtained at each unit operation of the recovery process. The recovery process includes

23、 physical separation that is freezing and thawing, centrifugation and filtration while the evaporation step is a method used to concentrate the recovered organic acids by eliminating excess water. The organic acids co

24、ntent increased by about 56% while the total suspended solids decreased by about 62.2% after the fermentation. By the freezing and thawing process, the organic acids content increased by 16% with 66% removal of total

25、suspended solids. The centrifugation and filtration process do not have an effect on the concentration of the organic acids. The total suspended solids decreased from 17.89 to 12.27 g/L. Water was evaporated at 50

26、76; C in vacuum and the remaining organic acids and some suspended solids were concentrated. After the evaporation step, both the organic acids and the total suspended solids contents were increased by 69 and 83%, re