HU195978B - Process for increacing the biogas producing capacity of fermentation system applying mixed bacterial pupulation - Google Patents

Abstract

To improve the capacity of biogas prodn. in a fermentation system, it is inoculated with a mixed population of bacteria, which in the presence of pyruvate-formate-lyase and formate-hydrogen-lyase enzymes and opt. with carbohydrate additives, produce hydrogen. Inoculation takes place at startup, initial progression or during the steady state of the process. - It is expedient to use a phylum of the Escherichia cloaceae species, pref. E.cloaceae-DSM 30054.

Description

The present invention relates to a process for increasing the biogas production capacity of a fermentation system using a mixed bacterial population. The process of the present invention, based on anaerobic fermentation, can be applied to biogas production technology of any organic feedstock (agricultural and industrial by-products, wastes, fertilizers and sludges from wastewater treatment).

It has long been known that microbial digestion of anaerobic digestible organic matter in the confined space produces methane-rich biogas. This degradation process is known to have three major steps. In the first step, macromolecules (proteins, fats, carbohydrates) are broken down by capable microorganisms. Among other things, sugars are formed. The sugars are fermented by another large group of bacteria into acetate, propionate, butyrate, CO2 and Hj gas in the second step. In particular, acetate, CO 3 and Hz serve as substrates for a third group of bacteria involved in fermentation, the methanogenic bacteria; the final product is methane-rich biogas (see, for example, Hobson, P.N. Bonsfield, S., Suraraers, R., "Methane Production, Agricultural and Domestic Wastes Applied Sci. Publ., London, 1981).

The bacteria involved in biogas fermentation, their living conditions and the conditions for their optimal functioning are only partially known. In particular, little data are available on the effect of bacteria in the mixed bacterial population in the fermenter. Therefore, when starting a biogas production process, they usually count on the growth of bacteria entering the system and spontaneous equilibration of the introduced organic matter, or inoculation with the "already functioning" fermentation material of a similar biogas production system to speed up the process. Even in the latter case, the bacterial yield is low, especially when compared to sterile fermentation technologies. The development of a bacterial population is not a controlled, uncertain process.

These shortcomings have a number of consequences for the efficiency of biogas production. Thus, reactor start-up is slow and not guaranteed to be successful, as the state of the bacterial population is most easily disrupted in this state.

However, in equilibrium biogas-producing, semi-continuous or continuous fermentation systems, the fermentation time is long, i.e. 25-30 days. Consequently, for example, the required fermentation reactor space is about thirty times the daily amount of waste.

We aim to eliminate the above disadvantages and to increase the efficiency and reliability of the biogas fermentation system by microbiological methods, so that our solution can be applied to the currently used biogas production technologies.

It has been found that the above objects are achievable if the spontaneous formation of each species of microorganism in the fermentation process utilizing the mixed bacterial population is maintained by inoculation of the microorganism producing the biogas by inoculation with a microorganism producing hydrogen gas by pyruvate formase lyase and formate hydrogenase lyase. It has also been found that an increased proportion of the microorganism introduced into the system by inoculation can be provided to an even greater extent and more generations by directly feeding its utilized nutrient into the fermentation system.

Accordingly, the present invention relates to a process for enhancing the biogas production capacity of a fermentation system using a mixed bacterial population. The process is characterized in that the system is inoculated with a pyruvate formase lyase and a formate hydrogenase lyase enzyme system at the start of fermentation and / or at the start-up stage and / or in the presence of a sugar-containing additive.

The microorganisms useful in the process of the invention are capable of decomposing the mono- and disaccharides to carbon dioxide and hydrogen. Their continuous formation as a substrate increases the number and activity of the methanogenic bacteria without the risk of an overproduction imbalance resulting in a deleterious effect on the acetogenic bacteria.

Preferably the microorganism used in the process of the invention is Enterobacter cloaceae, preferably Enterobacter cloaceae DSM 30054 (ATCC 13048).

In the method according to the invention, the inoculum culture of the microorganism is used in an amount of 5 to 20% by volume of its fermentation volume.

The sugar-containing additive optionally used in the process of the present invention is preferably molasses, preferably in the range of 1-5% by weight of the fermentation system.

For example, in the practice of the process according to the invention, (i) the microorganism used in the particular case is used to produce a monoculture at 30-37 ° C on a suitable medium known in the art, e.g. or on a sterile medium containing 6-carbon mono- or disaccharides or on an extract from a photosynthetic bacterium.

(ii) The available biomass (such as slurry or sludge from sewage sludge) is prepared using a Bmert technology of an anaerobic digestate to start the fermentation of the biogas.

(iii) The pure culture prepared according to (i) above is added to the fermentation biomass in a volume ratio of 1: 5 to 1:20.

(iv) As the fermentation progresses, the inoculation is repeated as needed during the start-up phase and / or at steady state (the steady state manifests itself in stabilization of gas evolution).

The main advantages of the process of the invention can be summarized as follows:

a) The process of the present invention provides a more reliable and faster way of starting and restarting biogas producing ferroentors.

b) The process according to the invention can reduce the fermentation time of biogas production processes and significantly increase the specific biogas yield.

c) During fermentation using the process according to the invention, the waste is perfectly decorticated, which reduces the environmental problems associated with the disposal of such waste.

d) The process according to the invention can be incorporated into existing biogas production technologies without any major modification.

e) In the process of the present invention, the biogas formed is hydrogen-enriched using a sugar-containing additive such as molasses.

The invention is illustrated by the following non-limiting examples.

Example 1

As raw material with the following characteristics

judge in cattle ranching formed of hollow we use: Dry matter content ⁸⁰ g / L Organic solids content 71 g / L pH 7.2 COD (chemical oxidation index) 77 g / L

The stock is filled into a 100 ml Erlenmeyer flask with a stopper, sealed with an amount of 50-50 ml. 5-5 ml of sterile 10 * cells / ml Escherichia cloaceae DSM 30 054 or dilution 1/10 or 1/100 in each flask are then added to each flask, while 20 ml of the same volume is added to control flasks. potassium phosphate buffer (pH 7.2-7.5) was added. The flasks are sealed and the air space above the liquid is replaced with oxygen-free nitrogen gas. The vessels were kept at constant temperature and stirred by constant shaking. The biogas produced is sequentially discharged, periodically sampled and gaseous chromatographed to determine the composition of the gas and the volume of biogas collected in the air. (The CH _t content of the biogas _is 60-65%.) Table 1 summarizes the composition and amount of gas produced by the inoculated and untreated samples:

Table 1

fermentation ττίΑΠ— - Production of gas (mmoles of gas per liter) TA tion time (Sun) Inoculum suspension (E. cloaceae cells / ml) roll 10 » 10 ' * 10 1 hj 2.1 2.1 3.5 4.3 CH «+ COj 12.3 23 39.4 126 8 hj 0 0 0 0 CH «+ COj 146 220 280 340 30 hj 0 0 0 0 CH, & COj 850 1300 2500 4100

The almost odorless product obtained after the fermentation is finished has the following characteristics:

solids content: 28-31 g / liters organic solids content: 20-24 g / liters pH: 5.2-6

COD: 30-34 g / l

The sterile culture medium for inoculation is prepared on a liquid medium containing 5.0 g peptone and 3.0 g meat extract in 1000.0 ml water. The pH of the medium was sterilized by heat treatment at 7.0 and 121 ° C for 15 minutes. This medium is inoculated with a stock of inoculum strains.

Example 2

All were carried out as described in Example 1 except that molasses was added to the inoculated samples. The seeding culture seed number was 10 * / ml. The results are shown in Table 2.

Table 2

Male Gas production (mmoles of gas / l) stallion - ------ ma- - molasses final concentration (%) time Kont (day) roll 0.4 2.5 10

Hj 2.4 7 622 500

1 CH «+ COj 14 33 29 0 δ hj 0 0 0 800 CO2 + CH4 160 200 542 0 30 hj 0 0 0 3000 CH. + COj 790 1800 9200 0

The last column of Table 2 shows that in the case of molasses overdose, a typical fermentation is produced which produces Hj.

The almost odorless product obtained after the completion of the fermentation has the following characteristics:

solids content: 31-60 g / liters organic solids content: 22-51 g / liters pH: 4.8-5.5

COD: 30-60 g / l

Example 3

The characteristics of Barkam slurry from pig farming as a raw material are as follows:

solids content: 50 g / l organic solids content: 37 g / l pH: 7.8

COD: 47 g / l

The procedures for handling and measuring the samples are as described in Example 1. The results are shown in Table 3.

Table 3

fermentation gas production (mmoles of gas per liter) TA Fire extinguisher suspension tion (E. cloaceae here- cells / ml) je a contrast (Sun) roll 10 » 10 '10 » Hz 1 2.4 2.8 4.2 5.5 CH4 + CO1 15 30 52,165

fermentation gas production (mmoles of gas per liter) you- inoculation suspension tion (E. cloaceae here- cells / ml, je a contrast (Sun) roll * 10 10 ' 10 » 8 hj 0 0 0 0 CH4 + CO1 202 294 383 476 30 hj 0 0 0 0 CH4 + CO1 960 1450 2640 5020 THE after fermentation received, almost smell-

The product characteristics of the dish are as follows: dry matter content: 12-16 g / liters organic solids content: 9-13 g / liters pH: 6.0-6.3

COD: 12-15 g / l

Example 4

All were carried out as described in Example 3, with the exception that molasses was added to the inoculated samples. The inoculum culture is a cell pattern of ΙΟ '/ ml. The results are shown in Table 4.

Table 4

Fermen Gas production (mmoles gauze / l) ¹ ----------- Molasses Final concentration here- (%)

je (Sun) contact roll 0.4 2.5 10 1 Hí 2.0 6.9 814 763 CH »+ COj 16.0 47 65 20 8 hj 0 0 0 934 CH. + COj 220 386 873 78 30 hj 0 0 0 675 CHI + COj 930 2500 10100 320

The almost odorless product obtained after fermentation has the following characteristics:

solids content: 16-30 g / l organic solids content: 12-25 g / l pll: 5.0-6.3

COD: 11-20 g / l

Claims (4)

PATENT CLAIMS A method for increasing the biogas production capacity of a fermentation system using a mixed bacterial population, comprising: inoculate, optionally in the presence of a sugar-containing additive. 2. The method of claim 1, wherein the microorganism is Escherichia cloaceae. The process according to claim 1 or 2, wherein the microorganism is Escherichia cloaceae DSM 30054. 4. The process according to any one of claims 1 to 3, wherein the culture of the microorganism is used in an amount of 5 to 20% by volume of the fermentation system. IQ 5. A process according to any one of claims 1 to 6, wherein the amount of sugar-containing additive is adjusted to 1-5% by weight of the fermentation system.