Lactic acid fermentation in Bioreactor

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Lactic acid fermentation in Bioreactor

Lactic acid fermentation in Bioreactor

CHEN 6701 Advanced reaction major Assignment

Z3353443

Tingying Zhu


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Executive Summary

Among all fermentation of lactic acid, whey fermentation is considered to be a low cost and most environmentally friendly method. The previous research on whey shows that lactose is the only carbohydrate in whey. Thus, this provides an advantage to ferment lactic acid form whey less side product and high yield. Because there only one product in the reaction.

Molecule Michaelis-Menten Equation (Monod equation) plays an important role in modeling bioreactor process. Most literature works are based on Monod equation. Thus, the model in this assignment is based on Monod equation. The plot is time as a function of concentration. Table 1. shows the equation used in this assignment.

Table 1. Model used in lactic acid fermentation

This article puts more emphasis on the influence of initial concentration and using two reactors instead of one reactor on lactic acid fermentation reaction. The model is based on the assumption that ignoring the death of cell and the culture in the reactor is well mixed. This assignment also discussed the influence of pH and temperature on the fermentation process. There exists an optimal temperature and pH value for bio-process, because the cell (Lactobacillus casei) is very sensitive to temperature and pH value. Although the model above did not cover the impact of temperature, this article still discussed the influence of them by using pervious work. Any modeling has its limitation. In this model, the parameter chooses is a very important part. Different parameter from literature has significant effect on the result.

The result shows initial substrate has significant impact on fermentation time and maximum concentration. According to the result, it shows the lower the initial concentration is, the longer the fermentation time will be in order to reach maximum production conversion. However, because the model is based on the concentration as function of time, temperature and ph value does not cover the reaction, and this function is assumed do not take into account the cell death process. Therefore, when the parameters are in different conditions, there will be some error in the production concentration. Overall, this article focuses on the initial concentration of lactic acid fermentation reactions important role. A suitable initial concentration can be high yield and shorten reaction time. This is exactly the reaction engineering to achieve the objective.

In part 5 and 6 parts, this assignment discussed the start up and shot down process of bioreactor and simple principle of scale up the reactor. In general, once the reaction start, only under the especially condition, the reactor will stop working. Thus, the start up and shut down is quit important. Furthermore, the reason to analysis the influence on reactor is to scale up the reactor, so that, the product could become commercial product. Therefore, how to make laboratory-scale reactor can be used in industrial production is the study of the role of reaction engineering(). In this part, it is simple introduction to the principles from geometry to enlarge, and stirring rate of amplification

At last part, it simply introduces some commercial use of lactic acid. As a commercial product, lactic acid has widely used in food, pharmaceutical industries, including poly lactic acid has been a lot of attention, and there are a number of related research is aimed at this area().

In conclusion, this paper is focus on analysis and modeling the factors affect on lactic acid fermentation in a bioreactor. Initial concentration, experimental parameters, pH and temperature have important influence on the yield of product. Nevertheless, some problems still must be solved for better performance to be obtained.


1. Introduction & Objectives

1.1Background

Lactic acid (2-hydroxypropanoic acid) was discovered in 1780 by the Swedish chemist Scheele in sour milk. Lactic acid is an important member of hydroxy acids group, and lactic usually is found in yogurt (). Moreover, animal muscle also contains lactic acid, when the muscles of lactic acid were the most tired state. Lactic acid is a commercial chemical production of fermentation. Lactic acid is widely used in the different area. The applications of lactic acid can be found in the food, drugs and medicine industries. It can miscible in water, ethanol, and glycerin and insoluble in chloroform, carbon disulfide and petroleum ether. Lactic acid can be used in many areas, such as preservation of foods, a flavoring agent and serve as sour agent. In addition, poly lactic acid is a biodegradable polymer, which instead of conversional plastic materials. The conventional synthesis methods are formed from acrylonitrile, propionic acid and propylene.().

Figure 1.1.1 L (+) Lactic acid and D (-) Lactic acid

Lactic acid has two optically active enantiomers, which are L-(+) lactic acid and D-(−) lactic acid. Figure 1.1.1 shows the two different chemical structure of lactic acid. Generally, fermentative process can selectively form L-lactic acid instead of a mixture of L and D product. In the production of lactic acid fermentation, the organisms from one isomer of lactic acid form the substrate. The yield of lactic acid is usually range of 80-90%().

1.2 Lactic acid fermentation

Fermentation is a very ancient practice, and the earliest literature can follow to 1000 years ago (). For the last decades, because the fossil fuel costs keeps increasing and the shortage of energy, fermentation technology got more and more attention and number of research is working on bioreactor (). In general, lactic acid can be produced by biomass, such as bacteria, yeasts, fugues and molds, and these process need to use carbohydrate as a substrates ().

Some search find that the production of L-lactic acid can be formed form corncob () and other types of organic materials. In industrial production, lactic acid commonly used of lactic acid bacteria fermentation of Lactobacillus and Lactobacillus Lai. In recent years, the use of Rhizopus oryzae to produce L-lactic acid has been reported, and the fermentation broth containing L-lactic acid la least 90%. Figure 1.2.1 is a simply process of lactic acid fermentation. It can be seen that the fermentation start from sugar. After a series of synthesis and chemical process, and ultimately the formation of lactic acid.

Figurte 1.2.1 Lactic acid fermentation.

In general, the process is carried out under atmospheric pressure at room temperature. Within this condition, the reaction is usually safety and simple operation. The raw materials used in fermentation are starch, molasses, or other agricultural-based and react with some organic and inorganic nitrogen. Due to different nutrition requirements, different microorganisms can be used to ferment products. Based on feature, we can use waste water and waste material to produce products. Because fermentation has very especial property, it usually only forms one product. Industrial fermentation, compared with other industries, less investment, quick, open can achieve significant economic benefits. Based on the above characteristics, industrial fermentation gain more attention. Compared with traditional fermentation process, fermentation engineering has more characteristics and advantages than the conventional ones.

Several methods has been reported to ferment lactic acid, such as extracting from solvent, membrane bioreactor, reverse osmosis and ion exchange (). Even the waste water can ferment lactic acid in early study. In addition, using corncob is also an available way to form lactic acid. Glucose or sucrose are generally certain raw materials for lactic acid fermentation processes on the basis of cost, availability, purity, and ease of product recovery.

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Corn flour with water is saccharificated and liquefied by high pressure jet, and mashing is pumped into plate and frame and then filtered. Residue are used as feed and clean sugar are pulled into the fermenter. By adjusting the concentration of sugar, the fermentation period is about 55~75h, and the conversion rate is not less than 90%().
That lactic acid pathway of glucose metabolism including the way in anaerobic and aerobic conditions. Glucose as raw material technologies is used to produce racemic DL-lactic acid, 0.375% malt,0.25%  (NH4)2HPO4 , 74.375% H2O, 10% CaCO3 as buffer, adjusting pH5.8~6, under 49oC, and the ...

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