JP2009082029A - Membrane bioreactor for continuously producing valuable resources through fermentation - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a membrane bioreactor for continuously producing valuable resources through fermentation, capable of efficiently carrying out the large-scale continuous production of the valuables by membrane fermentation. <P>SOLUTION: The membrane bioreactor for continuous production of valuable resources by fermentation is obtained, by immersing rotating flat membranes that have 5 m<SP>2</SP>/m<SP>3</SP>or higher and 40 m<SP>2</SP>/m<SP>3</SP>or lower effective film area per volume of the membrane bioreactor. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing valuable materials using microorganisms such as bacteria, yeasts, molds and actinomycetes. More specifically, the present invention relates to a method for producing valuable materials by continuously culturing these microorganisms using a membrane bioreactor while retaining / refluxing the cells.

  As a technology that can dramatically improve the speed of fermentation production, cells such as microorganisms and cultured cells are filtered through a separation membrane in a continuous fermentation method, and the filtered cells are collected at the same time as collecting the product from the membrane permeate. Has been proposed in which, for example, Patent Documents 1 to 3 have been proposed in which the cells are maintained or refluxed in a culture solution to increase the cell concentration in the culture solution. These membrane bioreactors have a membrane separation part outside the fermenter to circulate and filter (external circulation method), and a membrane to immerse the membrane in the fermenter and filter in a single tank (immersion method) ) Conventionally, when producing small-scale and expensive valuables, an external circulation method using exclusively hollow fiber membranes has been adopted, but when the production of general-purpose chemical products in biorefinery is considered Since it is necessary to keep production costs lower, it is considered advantageous to use an immersion method that can simplify and reduce the size of the equipment, and that does not require the power of the liquid circulation pump and can reduce the operation cost. Production equipment such as fermenters, piping, and pumps is particularly expensive due to the sanitary specifications, and the proportion of depreciation in the production cost is large. Also, the pressure loss due to flowing the circulating fluid through the hollow fiber membrane module is large. The immersion method is considered advantageous because it requires a large amount of power.

  Here, when trying to make fermentation production more efficient by increasing the reaction rate / increasing the amount of filtered water using a normal immersion membrane bioreactor in which flat membranes and hollow fiber membranes are immersed, It is necessary to improve the filling rate of the membrane element into the tank and the membrane surface cleaning power. When separating microorganisms with membranes, the filtration rate decreases due to microorganisms adhering to the membrane surface. Therefore, shearing force is applied to the membrane surface, and membrane separation is performed while removing microorganisms. When a flat membrane or hollow fiber membrane having a surface area of 1 mm is immersed in the fermenter, it becomes difficult to impart a water flow to the membrane element for the purpose of washing the membrane surface, and there is a problem that it does not lead to an improvement in water permeability as a whole membrane facility.

  On the other hand, in the method of increasing the filtration rate by applying a stronger water flow with a propeller or the like without changing the membrane area, a large amount of liquid must be circulated on the membrane surface, and a large amount of power is required for circulation. In addition to the necessity, liquid mixing of the entire fermentation broth becomes intense, causing stress on microorganisms, resulting in dead cells, cell wall polysaccharides, proteins, foam components, etc., leading to accelerated filterability and impurity concentration deterioration of the fermentation broth. It falls into a situation where continuous fermentation for a period becomes difficult.

As a promising filtration and separation technique that may eliminate this drawback, the flow rate of the microbial suspension is adjusted with respect to the membrane surface by rotating the membrane in the liquid instead of flowing the microbial suspension on the membrane surface. A rotating flat membrane type membrane separation device is proposed in the field of wastewater treatment, which generates a relative force and applies a shearing force to the membrane surface to remove microorganisms from the membrane surface to increase the filtration rate (Patent Literature). 4). This device can efficiently apply shear force and centrifugal force to the membrane surface by rotating the rotating flat membrane, and can remove microorganisms, so that the filtration rate can be increased, and the rotating speed of the rotating flat membrane can be increased. It is possible to increase the filtration rate by changing, but it is an excellent technology, but unlike the wastewater treatment for the purpose of decomposing unnecessary materials, in the fermentation field for the production of valuable materials, production by fermentation There is a suitable range for the rate and the supply rate of the medium as a raw material and the volume of the reactor, and in continuous membrane fermentation at a high production rate, no technology relating to the optimal effective membrane area per bioreactor volume has been disclosed . In particular, in fermentation production, there are microorganisms that are vulnerable to shear stress and fermentation liquids that have a high viscosity of the liquid. There has been a problem that the liquid filterability and the impurity concentration are accelerated and the long-term continuous fermentation becomes difficult.
Japanese Patent Publication No. 6-69367 JP-A 61-199793 JP 61-254184 A JP-A-62-97607

  As described above, in the conventional membrane bioreactor for continuous fermentation production of valuable resources, there has been no apparatus that can be suitably employed when large-scale production of a general chemical product in a biorefinery is carried out. An object of the present invention is a membrane for continuous fermentation production of valuable resources capable of efficiently realizing large-scale continuous membrane fermentation production at a high production rate (for example, 5 STY: Space Time Yield or more) without excessive membrane area or power. It is to provide a bioreactor.

  In order to solve the above problems, the present invention has the following configuration.

A membrane bioreactor for continuous production of valuable materials, in which a rotating flat membrane having an effective membrane area per membrane bioreactor volume of 5 m ² / m ³ or more and 40 m ² / m ³ or less is immersed.

  Continuous membrane fermentation production of organic acid production at high production rate and high filtration rate can be realized efficiently and stably.

  FIG. 1 shows a conceptual diagram of the membrane bioreactor for continuous production of valuable resources according to the present invention, but the shape, configuration, arrangement, etc. are not limited to this figure.

  The membrane bioreactor for continuous production of valuable resources has a bioreactor 1 for fermenting the medium 3 with microorganisms, and a rotating flat membrane 2 for separating microorganisms for microfiltration or ultrafiltration of the fermentation broth. The rotating flat membrane 2 is disposed inside the bioreactor 1, and a fermentation liquid mixing blade 6 is attached to the outer periphery of a part of the rotating flat membrane 2. A baffle plate 5 is provided inside the bioreactor 1. The membrane permeate filtered through the rotary flat membrane 2 is discharged out of the bioreactor by the driving force of the suction pump through the hollow rotary shaft 4 that also serves as a water collection pipe. The bioreactor 1 is provided with oxygen supply means, measuring equipment such as pH, DO, ORP sensor, and means for extracting the fermentation broth for sampling purposes as required (not shown).

At this time, as a result of earnest research, a membrane bioreactor in which a rotating flat membrane accommodates an effective membrane area of 10 m ² / m ³ or more per bioreactor volume has low power and cost associated with the membrane area, and has excellent operational stability. It was found that it was in the form of a membrane bioreactor for continuous fermentation production of valuable resources.

  Here, the rotating flat membrane is provided with a microorganism filtration function in which a plurality of hollow rotating shafts forming a flow path of membrane permeated water are installed at a predetermined interval and rotate integrally with the hollow rotating shaft. A flat membrane fixed on a flat plate. The shape of the flat plate / flat membrane is not particularly limited, and examples thereof include a circle, a regular hexagon, a polygon, a fan, and a trapezoid. However, a cylindrical bioreactor is used, and a hollow center is formed in the bioreactor. When a rotating shaft is provided and a circular rotating flat membrane is provided, the filtration performance as a membrane bioreactor is maximized, which is an example of a preferred embodiment.

Effective area of the rotary flat membrane which houses the bioreactor can wasted space inside the bioreactor is too low, be a capital cost increase, 5 m 2 ^/ m since too large, the film cost is increased disadvantageously ^{It is 3} or more and 40 m ² / m ³ or less, more preferably 12 m ² / m ³ or more and 30 m ² / m ³ or less, and further preferably 15 m ² / m ³ or more and 25 m ² / m ³ or less.

  A baffle plate may be inserted between the rotating flat membranes for the purpose of preventing co-circulation of the liquid.

  Liquid mixing in the bioreactor may be promoted by providing a rotating liquid membrane or a fermented liquid mixing blade connected to the rotating shaft of the rotating flat film and rotating at the same angular velocity as the rotating flat film.

  The rotation speed of the rotating flat membrane may be an amount necessary to obtain a predetermined flux according to the filterability of the fermentation broth, the concentration of microorganisms, the operation time, and the like. Further, the transmembrane pressure difference may be measured, and filtration may be performed by controlling the rotation speed so that the transmembrane pressure difference is maintained at a predetermined value or less.

The conceptual diagram of the membrane bioreactor of this invention is shown.

Explanation of symbols

1: Bioreactor 2: Rotating flat membrane 3: Medium 4: Hollow rotating shaft 5: Baffle plate 6: Fermentation liquid mixing blade

Claims (1)

A membrane bioreactor for continuous production of valuable materials, in which a rotating flat membrane having an effective membrane area per membrane bioreactor volume of 5 m ² / m ³ or more and 40 m ² / m ³ or less is immersed.

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