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Bioaugmentation of Lactobacillus delbrueckii ssp. bulgaricus TISTR 895 to enhance bio-hydrogen production of Rhodobacter sphaeroides KKU-PS5.

Laocharoen S, Reungsang A, Plangklang P - Biotechnol Biofuels (2015)

Bottom Line: A suitable LAB/PNSB ratio and initial cell concentration were found to be 1/12 (w/w) and 0.15 g/L, respectively.The ratio of the strains TISTR 895/KKU-PS5 and their initial cell concentrations affected the rate of lactic acid production and its consumption.A suitable LAB/PNSB ratio and initial cell concentration could balance the lactic acid production rate and its consumption in order to avoid lactic acid accumulation in the fermentation system.

View Article: PubMed Central - PubMed

Affiliation: Department of Biotechnology, Faculty of Technology, Khon Kaen University, Khon Kaen, 40002 Thailand.

ABSTRACT

Background: Bioaugmentation or an addition of the desired microorganisms or specialized microbial strains into the anaerobic digesters can enhance the performance of microbial community in the hydrogen production process. Most of the studies focused on a bioaugmentation of native microorganisms capable of producing hydrogen with the dark-fermentative hydrogen producers while information on bioaugmentation of purple non-sulfur photosynthetic bacteria (PNSB) with lactic acid-producing bacteria (LAB) is still limited. In our study, bioaugmentation of Rhodobacter sphaeroides KKU-PS5 with Lactobacillus delbrueckii ssp. bulgaricus TISTR 895 was conducted as a method to produce hydrogen. Unfortunately, even though well-characterized microorganisms were used in the fermentation system, a cultivation of two different organisms in the same bioreactor was still difficult because of the differences in their metabolic types, optimal conditions, and nutritional requirements. Therefore, evaluation of the physical and chemical factors affecting hydrogen production of PNSB augmented with LAB was conducted using a full factorial design followed by response surface methodology (RSM) with central composite design (CCD).

Results: A suitable LAB/PNSB ratio and initial cell concentration were found to be 1/12 (w/w) and 0.15 g/L, respectively. The optimal initial pH, light intensity, and Mo concentration obtained from RSM with CCD were 7.92, 8.37 klux and 0.44 mg/L, respectively. Under these optimal conditions, a cumulative hydrogen production of 3396 ± 66 mL H2/L, a hydrogen production rate (HPR) of 9.1 ± 0.2 mL H2/L h, and a hydrogen yield (HY) of 9.65 ± 0.23 mol H2/mol glucose were obtained. KKU-PS5 augmented with TISTR 895 produced hydrogen from glucose at a relatively high HY, 9.65 ± 0.23 mol H2/mol glucose, i.e., 80 % of the theoretical yield.

Conclusions: The ratio of the strains TISTR 895/KKU-PS5 and their initial cell concentrations affected the rate of lactic acid production and its consumption. A suitable LAB/PNSB ratio and initial cell concentration could balance the lactic acid production rate and its consumption in order to avoid lactic acid accumulation in the fermentation system. Through use of appropriate environmental conditions for bioaugmentation of PNSB with LAB, a hydrogen production could be enhanced.

No MeSH data available.


Related in: MedlinePlus

Variations of cumulative hydrogen production, concentrations of cell, glucose, and volatile fatty acid over time. Lactic acid-producing bacteria (LAB) only (LAB concentration = 0.019 g/L) (a); purple non-sulfur photosynthetic bacteria (PNSB) only (PNSB concentration = 0.131 g/L) (b); LAB/PNSB ratio of 1/12 at initial cell concentration of 0.15 g/L (LAB concentration = 0.019, PNSB concentration = 0.131 g/L) (c). Hydrogen (black circle), glucose (red triangle), cell (blue diamond), lactic acid (green square), formic acid (blue cross)
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Fig2: Variations of cumulative hydrogen production, concentrations of cell, glucose, and volatile fatty acid over time. Lactic acid-producing bacteria (LAB) only (LAB concentration = 0.019 g/L) (a); purple non-sulfur photosynthetic bacteria (PNSB) only (PNSB concentration = 0.131 g/L) (b); LAB/PNSB ratio of 1/12 at initial cell concentration of 0.15 g/L (LAB concentration = 0.019, PNSB concentration = 0.131 g/L) (c). Hydrogen (black circle), glucose (red triangle), cell (blue diamond), lactic acid (green square), formic acid (blue cross)

Mentions: We conducted experiments to investigate the effects of LAB only, PNSB only, and PNSB augmented with LAB on cumulative hydrogen production, biomass, glucose, and VFA concentrations under the optimal LAB/PNSB ratio of 1/12 and an initial cell concentration of 0.15 g/L. The results demonstrated that LABs cultured alone consumed glucose for cell maintenance and produced lactic acid as their primary product without hydrogen production (Fig. 2a). PNSB cultured alone consumed glucose for cell growth and hydrogen production with the cumulative hydrogen production, HPR, and HY of 1682 ± 76 mL H2/L, 3.2 ± 0.1 mL H2/L h, and 4.38 ± 0.20 mol H2/mol glucose, respectively (Fig. 2b). Formic acid was found in the hydrogen fermentation by PNSB (Fig. 2b). Normally, under light illumination, PNSB will not produce formic acid. However, our results showed that formic acid was produced at approximately 0.4 g/L (Fig. 2b) in the PNSB only fermentation. This may have been caused by high cell concentrations (approximately 1.8 g/L) (Fig. 2b) which could make the medium opaque, restricting light from entering the serum bottle, resulting in a light-limited condition in the system. Therefore, the metabolism of KKU-PS5 to metabolize glucose might have adapted to dark or limited light conditions resulting in formic acid formation. Our results are similar to the findings of Eroglu et al. [44] who found that under limited illumination, hydrogen was not produced by R. sphaeroides, but formate was produced as an end-product.Fig. 2


Bioaugmentation of Lactobacillus delbrueckii ssp. bulgaricus TISTR 895 to enhance bio-hydrogen production of Rhodobacter sphaeroides KKU-PS5.

Laocharoen S, Reungsang A, Plangklang P - Biotechnol Biofuels (2015)

Variations of cumulative hydrogen production, concentrations of cell, glucose, and volatile fatty acid over time. Lactic acid-producing bacteria (LAB) only (LAB concentration = 0.019 g/L) (a); purple non-sulfur photosynthetic bacteria (PNSB) only (PNSB concentration = 0.131 g/L) (b); LAB/PNSB ratio of 1/12 at initial cell concentration of 0.15 g/L (LAB concentration = 0.019, PNSB concentration = 0.131 g/L) (c). Hydrogen (black circle), glucose (red triangle), cell (blue diamond), lactic acid (green square), formic acid (blue cross)
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4660636&req=5

Fig2: Variations of cumulative hydrogen production, concentrations of cell, glucose, and volatile fatty acid over time. Lactic acid-producing bacteria (LAB) only (LAB concentration = 0.019 g/L) (a); purple non-sulfur photosynthetic bacteria (PNSB) only (PNSB concentration = 0.131 g/L) (b); LAB/PNSB ratio of 1/12 at initial cell concentration of 0.15 g/L (LAB concentration = 0.019, PNSB concentration = 0.131 g/L) (c). Hydrogen (black circle), glucose (red triangle), cell (blue diamond), lactic acid (green square), formic acid (blue cross)
Mentions: We conducted experiments to investigate the effects of LAB only, PNSB only, and PNSB augmented with LAB on cumulative hydrogen production, biomass, glucose, and VFA concentrations under the optimal LAB/PNSB ratio of 1/12 and an initial cell concentration of 0.15 g/L. The results demonstrated that LABs cultured alone consumed glucose for cell maintenance and produced lactic acid as their primary product without hydrogen production (Fig. 2a). PNSB cultured alone consumed glucose for cell growth and hydrogen production with the cumulative hydrogen production, HPR, and HY of 1682 ± 76 mL H2/L, 3.2 ± 0.1 mL H2/L h, and 4.38 ± 0.20 mol H2/mol glucose, respectively (Fig. 2b). Formic acid was found in the hydrogen fermentation by PNSB (Fig. 2b). Normally, under light illumination, PNSB will not produce formic acid. However, our results showed that formic acid was produced at approximately 0.4 g/L (Fig. 2b) in the PNSB only fermentation. This may have been caused by high cell concentrations (approximately 1.8 g/L) (Fig. 2b) which could make the medium opaque, restricting light from entering the serum bottle, resulting in a light-limited condition in the system. Therefore, the metabolism of KKU-PS5 to metabolize glucose might have adapted to dark or limited light conditions resulting in formic acid formation. Our results are similar to the findings of Eroglu et al. [44] who found that under limited illumination, hydrogen was not produced by R. sphaeroides, but formate was produced as an end-product.Fig. 2

Bottom Line: A suitable LAB/PNSB ratio and initial cell concentration were found to be 1/12 (w/w) and 0.15 g/L, respectively.The ratio of the strains TISTR 895/KKU-PS5 and their initial cell concentrations affected the rate of lactic acid production and its consumption.A suitable LAB/PNSB ratio and initial cell concentration could balance the lactic acid production rate and its consumption in order to avoid lactic acid accumulation in the fermentation system.

View Article: PubMed Central - PubMed

Affiliation: Department of Biotechnology, Faculty of Technology, Khon Kaen University, Khon Kaen, 40002 Thailand.

ABSTRACT

Background: Bioaugmentation or an addition of the desired microorganisms or specialized microbial strains into the anaerobic digesters can enhance the performance of microbial community in the hydrogen production process. Most of the studies focused on a bioaugmentation of native microorganisms capable of producing hydrogen with the dark-fermentative hydrogen producers while information on bioaugmentation of purple non-sulfur photosynthetic bacteria (PNSB) with lactic acid-producing bacteria (LAB) is still limited. In our study, bioaugmentation of Rhodobacter sphaeroides KKU-PS5 with Lactobacillus delbrueckii ssp. bulgaricus TISTR 895 was conducted as a method to produce hydrogen. Unfortunately, even though well-characterized microorganisms were used in the fermentation system, a cultivation of two different organisms in the same bioreactor was still difficult because of the differences in their metabolic types, optimal conditions, and nutritional requirements. Therefore, evaluation of the physical and chemical factors affecting hydrogen production of PNSB augmented with LAB was conducted using a full factorial design followed by response surface methodology (RSM) with central composite design (CCD).

Results: A suitable LAB/PNSB ratio and initial cell concentration were found to be 1/12 (w/w) and 0.15 g/L, respectively. The optimal initial pH, light intensity, and Mo concentration obtained from RSM with CCD were 7.92, 8.37 klux and 0.44 mg/L, respectively. Under these optimal conditions, a cumulative hydrogen production of 3396 ± 66 mL H2/L, a hydrogen production rate (HPR) of 9.1 ± 0.2 mL H2/L h, and a hydrogen yield (HY) of 9.65 ± 0.23 mol H2/mol glucose were obtained. KKU-PS5 augmented with TISTR 895 produced hydrogen from glucose at a relatively high HY, 9.65 ± 0.23 mol H2/mol glucose, i.e., 80 % of the theoretical yield.

Conclusions: The ratio of the strains TISTR 895/KKU-PS5 and their initial cell concentrations affected the rate of lactic acid production and its consumption. A suitable LAB/PNSB ratio and initial cell concentration could balance the lactic acid production rate and its consumption in order to avoid lactic acid accumulation in the fermentation system. Through use of appropriate environmental conditions for bioaugmentation of PNSB with LAB, a hydrogen production could be enhanced.

No MeSH data available.


Related in: MedlinePlus