Development of L-Phenylalanine in China   

By Ding Rui and Ao Yonghua, Shenyang Agricultural University

L-phenylalanine is an important amino acid and also one of eight essential amino acids for the human body. It can also be used as an intermediate or carrier for some anti-cancer drugs. With the growing consumption of low-calorie and high-intensity sweetener aspartame, the demand for L-phenylalanine, the main raw material of aspartame, is constantly increasing. Before 1998, although there was a huge demand for L-phenylalanine in China, due to the lack of industrial production technology for this product, China's L-phenylalanine market was completely dependent on imports. In order to alleviate the contradiction between the supply and demand of the domestic L-phenylalanine market, the research and development of the L-phenylalanine production process were included in China's major national scientific research programs during 1991-2005. After nearly 20 years of development, China's L - phenylalanine industry has now been able to meet the domestic demand.

1 Evolution of L-phenylalanine production technology in China

Overall, the production processes of L-phenylalanine mainly include: the natural proteolysis method, the chemical synthesis method, the enzymatic method and the fermentation method. Their evolution in China is listed in Table 1.

Table 1 Evolution of L-phenylalanine production technology in China
Year    Technology    Capacity (t/a)    Production cost (RMB /t)    Remarks
Prior to 1998    Natural proteolysis method    Very little    Very high    Domestic L-phenylalanine market was totally dependent on imports
1998    Cinnamic acid enzymatic process    100    120 000    Due to high cost and impacts of low-cost imports, plants built with the process were all shut down by 2005
2009    Direct fermentation method    5 000    30 000    This process now dominates L-phenylalanine production in China, with a total capacity of more than 15 000 t/a

    Before 1998, China mainly used the natural proteolysis method to produce L-phenylalanine. But this production process is relatively complex and has unstable product quality and is difficult for the industrial production. So the domestic L-phenylalanine production was far from satisfying the domestic demand at that time.
   In 1998, Chinese scientists at the Chengdu Institute of Biology of the Chinese Academy of Sciences developed an enzyme-based L-phenylalanine production process, that is, the cinnamic acid / red yeast phenylalanine ammonia-lyase (PAL) whole-cell reverse biocatalytic enzyme process (briefly called the cinnamic acid enzymatic process). At the same year, this institution and Shaoxing Yamei Biochemistry Co Ltd (Yamei Biochem) jointly built China's first 100 t/a L-phenylalanine production line with this process. This effectively eased the contradiction between the supply and demand of L-phenylalanine in China. It also marks the beginning of L-phenylalanine industrial production in the country. At the same time, Chinese scientists also developed the Hein-phenylketonuria enzymatic process for the industrial production of L-phenylalanine. Compared to the Hein-phenylketonuria enzymatic process, the main raw material (cinnamic acid) of the cinnamic acid enzymatic process is more easily available and more stable. So the cinnamic acid enzymatic process was the main production process of L-phenylalanine in China at that time. The production cost of L-phenylalanine by this process is more than RMB120 000 /t.
   At the same time, Chinese scientists were also developing the fermentation process for the industrial production of L-phenylalanine. But they lacked proprietary high-L-phenylalanine-yielding bacteria. Their fermentation processes were not mature and were not suitable for industrial production at that time.
   In the end of 2001, China formally joined the World Trade Organization (WTO). With more opportunities, Chinese enterprises were also faced with greater challenges. Under impacts of low-cost imported L-phenylalanine products, China's enzyme-based L-phenylalanine production lines were all shut down by 2005 due to high production costs. China's fledgling L-phenylalanine industry suffered a big blow.
   In 2009, this situation was finally broken by two professors at the Engineering Research Center for Industrial Microbiology, Fujian Normal University. They invented the direct fermentation method. They used the metabolic engineering principle to transform the original fermentation strains at the cellular level, and applied the directed molecular coevolution technology to transform the genes, aroG and pheA, of the key enzyme in the L-phenylalanine metabolic pathway and constructed a mutant library, thus screening out a high- L-phenylalanine-yielding mutant strain. Later, Fujian Maidan Biology Co Ltd used the mutant strain in the industrial production of L-phenylalanine. In 2009 alone, the company produced 5 000 tons of L-phenylalanine. Its L-phenylalanine output ranked second in the world, only next to Japan's Ajinomoto, and ranked first in China. The production cost of L-phenylalanine by this process drops to less than RMB30 000/t, well lower than those of international L-phenylalanine products. Under the dual strikes of China's low-cost L-phenylalanine products and the global financial crisis, the operation rate of L-phenylalanine producers in Japan and the USA has fallen below 50%.

2 Production of L-phenylalanine in China

Currently, the largest L - phenylalanine producer in China is Fujian Maidan Biology Co Ltd (Maidan Biology). Fuzhou Fuxing Pharmaceutical Co Ltd (Fuxing Pharm) is the second largest. Both are located in East China's Fujian Province. Maidan Biology has an L - phenylalanine capacity of about 9 000 t/a, accounting for more than 60% of China's total. Fuxing Pharm has a capacity of about 4 000 t/a. Other producers, such as Jiangsu Hanguang Group and Liyang Vitasweet Co Ltd, also have a small amount of L-phenylalanine production, but their products are mainly for their own uses, used to produce aspartame. Major L-phenylalanine producers in China are listed Table 2.

Table 2 Major L-phenylalanine producers in China
Producer    Capacity (t/a)    Remark
Fujian Maidan Biology Co Ltd    9 000    Sell L-phenylalanine to the market
Fuzhou Fuxing Pharmaceutical Co Ltd    4 000    Sell L-phenylalanine to the market
Jiangsu Hanguang Group       500    For own use; used to produce aspartame
Liyang Vitasweet Co Ltd       300    For own use; used to produce aspartame
Hangzhou Dongchen Bioengineering Co Ltd       200    For own use


3 Consumption of L-phenylalanine in China

The domestic market demand for L-phenylalanine mainly comes from aspartame manufacturers. More than 80% of L-phenylalanine is used to produce aspartame in China.
   In 2010, China's total demand for L-phenylalanine was about 12 000 tons, of which about 9 500 tons was used to produce aspartame, 2 000 tons was used for amino acid infusion and pharmaceutical intermediates, and 500 tons was used in feed additives, food additives, nutritional additives and synthetic vitamins.
   In China