**1. Introduction**

The gases which bring greenhouse effect are water vapor and trace gases in atmosphere, carbon dioxide (CO2), methane (CH4), nitrous oxide (N2), sulfur hexafluoride (SF6), hydrofluorocarbons (HFCs), and perfluorocarbons (PFCs). Global warming due to increases in the atmospheric concentration of greenhouse gases (GHG) is an important issue. The worldwide trends of carbon dioxide have shown an increase in the greenhouse effect on global warming (Houghton, 1994). However, CH4 is an important greenhouse gas second only to CO2 in its contribution to global warming due to its high absorption ability of infrared in the radiation from sun (IPCC, 1994). The world population of ruminants is important source of methane, contributing approximately 15-18% of the total atmospheric CH4 flux. The control of CH4 emission is a logical option since atmospheric CH4 concentration is increasing at a faster rate than carbon dioxide (Moss, 1993). CH4 emitted from ruminants is mainly generated in the rumen by hydrogenotrophic methanogens that utilize hydrogen to reduce carbon dioxide, and is a significant electron sink in the rumen ecosystem (Klieve and Hegarty, 1999), although acetotrophic methanogens may play a limited role for rumen methanogenesis (McAllister, 1996). Methane contains 892.6 kJ combustible energy per molecule at 25ºC and 1013hPa, while not contributing to the total supply of metabolic energy to ruminants (Takahashi *et al*., 1997). As reported by Leng (1991), methane production from ruminants in the developing countries may be high since the diets are often deficient in critical nutrients for efficient microbial growth in the rumen. So far, a number of inhibitors of methanogenesis have been developed to improve feed conversion efficiency of ruminant feeds claimed to be effective in suppressing methanogens or overall bacterial activities (Chalupa, 1984). Attempts to reduce methanogenesis by the supplementation of chemicals such as ionophores (monensin and lasalocid), have long been made (Chalupa, 1984; Hopgood and Walker, 1967). However, these ionophores may depress

© 2013 Takahashi, licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2013 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

fiber digestion and protozoal growths (Chen and Wolin, 1979). In addition, some resistant bacteria will appear in the rumen from the results of long term use of the ionophores. Therefore, development of manipulators to mitigate rumen methanogenesis must pay attention to secure safety for animals, their products and environment as alternatives of ionophores.

Lactic Acid Bacteria and Mitigation of GHG Emission from Ruminant Livestock 457

Lys Abu

15

Ser Ala His

Gly

Ala

S

Ala Met

Leu

S

Gly

Ala

Asn

Lys

Abu

Abu Ala

S

25

Met

20

Dha = dehydroalanine, Dhb = dehydrobutyrine, Ala-S-Ala = lanthionine, Abu-S-Ala = β-methyllanthionine. (adapted

Pro Gly

S

10

Ala

**2. Possible control of indirect action of lactic acid bacteria as probiotics** 

Rumen manipulation with ionophores such as monensin has been reported to abate rumen methanogenesis (Mwenya *et al*., 2005), However, there is an increasing interest in exploiting prebiotics and probiotics as natural feed additives to solve problems in animal nutrition and livestock production as alternatives of the antibiotics due to concerns about incidences of resistant bacteria and environmental pollution by the excreted active-antibacterial substances (Mwenya *et al*., 2006). Particular interest concerning bacteriocins which produced

Bacteriocins, antimicrobial proteinaceous polymeric material substances, are ubiquitous in nature being produced by a variety of Gram-negative and Gram-positive bacteria, and typically narrow spectrum antibacterial substances under the control of plasmid. Nisin is produced by *Lactococcus lactis* ssp. *lactis* which is an amphiphilic peptide composed by 34 amino acids with two structural domains that are connected by a flexible hinge (Breukink *et al*., 1998; Montville and Chen, 1998), and is classified into the group of lantibiotics. Nisin has a mode of action similar to ionophores, which show antimicrobial activity against a broad spectrum of Gram-positive bacteria and is widely used in the food industry as a safe and natural preservative (Delves-Broughton *et al*., 1996). It is generally recognized as safe (GRAS) and given international acceptance in 1969 by the joint Food and Agriculture Organization/World Health Organization (FAO/WHO) Expert Committee on Food

from Breukink et al., 1998).

Ile

1

NH2

Dhb Ala

Trp

**Figure 1.** Primary structure of nisin.

S

HOOC

Dha

5

Leu

Ala Abu

Trp

Lys Val Dha His Ile

Ser

34 30

Ile

**on rumen methanogenesis** 

by lactic acid bacteria has increased recently.

Theoretically, methanogenesis can be reduced by either a decrease in the production of H2, the major substrates for methane formation or an increase in the utilization of H2 and formate by organisms other than methanogens. However, direct inhibition of H2-forming reactions may depress fermentation in microorganisms that produce H2, including main cellulolytic bacteria such as *Ruminococcus albus* and *Ruminococcus flavefaciens* (Belaich *et al.,* 1990; Wolin, 1975). Therefore, a reduction in H2 production by the enhancement of reactions that accept electrons is desirable (Stewart and Bryant, 1988). In the rumen, metabolic H2 is produced during the anaerobic fermentation of glucose. This H2 can be used during the synthesis of volatile fatty acids and microbial organic matter. The excess H2 from NADH is eliminated primarily by the formation of CH4 by methanogens, which are microorganisms from the *Archea* group that are normally found in the rumen ecosystem (Baker, 1999). The stoichiometric balance of VFA, CO2 and CH4 indicates that acetate and butyrate promote CH4 production whereas propionate formation conserves H2, thereby reducing CH4 production (Wolin, and Miller, 1988). By contrast, reductive methanogenesis might contribute to mitigate methane (Immig *et al*., 1996). Therefore, a strategy to mitigate ruminal CH4 emission is to promote alternative metabolic pathway to dispose the reducing power, competing with methanogenesis for H2 uptake. Oligosaccharides are naturally occurring carbohydrates with a low degree of polymerisation and consequently low molecular weight, being commonly found to perform in the various plant and animal sources. 1-4 Galactooligosaccharides (GOS) are non-digestible carbohydrates, which are resistant to gastrointestinal digestive enzymes, but fermented by specific colonic bacteria. The products of fermentation of GOS in the colon, mainly short chain fatty acids, have a role in the improvement of the colonic environment, energy supply to the colonic epithelium, and calcium and magnesium absorption (Sako, *et al*., 1999). The indigestibility and stability of GOS to hydrolysis by -amylase of human saliva, pig pancreas, rat small intestinal contents and human artificial gastric juice has been shown in several *in vitro* experiments (Ohtsuka *et al*., 1990; Watanuki *et al*., 1996). This is because GOS have -configuration, whereas human gastrointestinal digestive enzymes are mostly specific for -glycosidic bonds. From this point of view, expectedly, GOS will be readily degraded in the rumen as a result of the ruminal enzymes being specific for -glycosidic bonds. Thus, lactic acid bacteria may consume GOS to promote propionate formation through acrylate pathway, and consequently the competition with methanogens for hydrogen will occur. Thus, the amplifying competition of metabolic H2 with probiotics may be a key factor in the regulation of rumen methanogenesis. However, direct effects of prebiotics and secondary metabolites such as tannin, saponin and natural resin on methanogens and eubacteria in the rumen remain to be elucidated to secure the safety for animals, their products and environment. The mechanism for accreditation of manipulators must be established to mitigate global CH4 emission.

Dha = dehydroalanine, Dhb = dehydrobutyrine, Ala-S-Ala = lanthionine, Abu-S-Ala = β-methyllanthionine. (adapted from Breukink et al., 1998).

**Figure 1.** Primary structure of nisin.

456 Lactic Acid Bacteria – R & D for Food, Health and Livestock Purposes

manipulators must be established to mitigate global CH4 emission.

ionophores.

fiber digestion and protozoal growths (Chen and Wolin, 1979). In addition, some resistant bacteria will appear in the rumen from the results of long term use of the ionophores. Therefore, development of manipulators to mitigate rumen methanogenesis must pay attention to secure safety for animals, their products and environment as alternatives of

Theoretically, methanogenesis can be reduced by either a decrease in the production of H2, the major substrates for methane formation or an increase in the utilization of H2 and formate by organisms other than methanogens. However, direct inhibition of H2-forming reactions may depress fermentation in microorganisms that produce H2, including main cellulolytic bacteria such as *Ruminococcus albus* and *Ruminococcus flavefaciens* (Belaich *et al.,* 1990; Wolin, 1975). Therefore, a reduction in H2 production by the enhancement of reactions that accept electrons is desirable (Stewart and Bryant, 1988). In the rumen, metabolic H2 is produced during the anaerobic fermentation of glucose. This H2 can be used during the synthesis of volatile fatty acids and microbial organic matter. The excess H2 from NADH is eliminated primarily by the formation of CH4 by methanogens, which are microorganisms from the *Archea* group that are normally found in the rumen ecosystem (Baker, 1999). The stoichiometric balance of VFA, CO2 and CH4 indicates that acetate and butyrate promote CH4 production whereas propionate formation conserves H2, thereby reducing CH4 production (Wolin, and Miller, 1988). By contrast, reductive methanogenesis might contribute to mitigate methane (Immig *et al*., 1996). Therefore, a strategy to mitigate ruminal CH4 emission is to promote alternative metabolic pathway to dispose the reducing power, competing with methanogenesis for H2 uptake. Oligosaccharides are naturally occurring carbohydrates with a low degree of polymerisation and consequently low molecular weight, being commonly found to perform in the various plant and animal sources. 1-4 Galactooligosaccharides (GOS) are non-digestible carbohydrates, which are resistant to gastrointestinal digestive enzymes, but fermented by specific colonic bacteria. The products of fermentation of GOS in the colon, mainly short chain fatty acids, have a role in the improvement of the colonic environment, energy supply to the colonic epithelium, and calcium and magnesium absorption (Sako, *et al*., 1999). The indigestibility and stability of GOS to hydrolysis by -amylase of human saliva, pig pancreas, rat small intestinal contents and human artificial gastric juice has been shown in several *in vitro* experiments (Ohtsuka *et al*., 1990; Watanuki *et al*., 1996). This is because GOS have -configuration, whereas human gastrointestinal digestive enzymes are mostly specific for -glycosidic bonds. From this point of view, expectedly, GOS will be readily degraded in the rumen as a result of the ruminal enzymes being specific for -glycosidic bonds. Thus, lactic acid bacteria may consume GOS to promote propionate formation through acrylate pathway, and consequently the competition with methanogens for hydrogen will occur. Thus, the amplifying competition of metabolic H2 with probiotics may be a key factor in the regulation of rumen methanogenesis. However, direct effects of prebiotics and secondary metabolites such as tannin, saponin and natural resin on methanogens and eubacteria in the rumen remain to be elucidated to secure the safety for animals, their products and environment. The mechanism for accreditation of
