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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

Response surface plots showing the effects of initial pH, light intensity, and Mo concentration on hydrogen production rate (HPR). The interactive effect of light intensity and pH at a fixed the amount of Mo concentration of 0.44 mg/L (a); the interactive effect of Mo concentration and pH at a fixed light intensity of 8.37 klux (b); the interactive effect of Mo concentration and light intensity at a fixed pH of 7.92 (c)
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Fig3: Response surface plots showing the effects of initial pH, light intensity, and Mo concentration on hydrogen production rate (HPR). The interactive effect of light intensity and pH at a fixed the amount of Mo concentration of 0.44 mg/L (a); the interactive effect of Mo concentration and pH at a fixed light intensity of 8.37 klux (b); the interactive effect of Mo concentration and light intensity at a fixed pH of 7.92 (c)

Mentions: Response surface plots in three dimensions were developed based on Eq. (5) with one variable being kept constant at its optimal level, and varying the other two parameters over the experimental range (Fig. 3a–c). The highest points in Fig. 3 indicate the optimal conditions for maximal HPR. The HPR increased with the increasing light intensity from 6.00 to 8.37 klux and decreased at light intensities over 8.37 klux (Fig. 3a, c). Light provides ATP and reductive power to the photosynthetic system of photo-fermentative bacteria needed for the hydrogen production process [45]. However, excess light causes a saturation effect, in which ATP and Fd(red) were excessive for the available nitrogenase [2]. In addition, excess protons generated under high light intensities were captured by photo-fermentative bacteria and dissipated as heat energy, damaging their photosynthetic apparatus [46]. Consequently, a low HPR was obtained at high light intensity. Our previous research found that the optimal light intensity for the strain KKU-PS5 was 6 klux [32]. The higher optimal light intensity, from 6 to 8.37 klux, found in this study may be due to a shading effect of LAB and PNSB in the fermentation broth. Hence, higher light intensity is needed for hydrogen fermentation by bioaugmentation system than that by PNSB alone.Fig. 3


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)

Response surface plots showing the effects of initial pH, light intensity, and Mo concentration on hydrogen production rate (HPR). The interactive effect of light intensity and pH at a fixed the amount of Mo concentration of 0.44 mg/L (a); the interactive effect of Mo concentration and pH at a fixed light intensity of 8.37 klux (b); the interactive effect of Mo concentration and light intensity at a fixed pH of 7.92 (c)
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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

Fig3: Response surface plots showing the effects of initial pH, light intensity, and Mo concentration on hydrogen production rate (HPR). The interactive effect of light intensity and pH at a fixed the amount of Mo concentration of 0.44 mg/L (a); the interactive effect of Mo concentration and pH at a fixed light intensity of 8.37 klux (b); the interactive effect of Mo concentration and light intensity at a fixed pH of 7.92 (c)
Mentions: Response surface plots in three dimensions were developed based on Eq. (5) with one variable being kept constant at its optimal level, and varying the other two parameters over the experimental range (Fig. 3a–c). The highest points in Fig. 3 indicate the optimal conditions for maximal HPR. The HPR increased with the increasing light intensity from 6.00 to 8.37 klux and decreased at light intensities over 8.37 klux (Fig. 3a, c). Light provides ATP and reductive power to the photosynthetic system of photo-fermentative bacteria needed for the hydrogen production process [45]. However, excess light causes a saturation effect, in which ATP and Fd(red) were excessive for the available nitrogenase [2]. In addition, excess protons generated under high light intensities were captured by photo-fermentative bacteria and dissipated as heat energy, damaging their photosynthetic apparatus [46]. Consequently, a low HPR was obtained at high light intensity. Our previous research found that the optimal light intensity for the strain KKU-PS5 was 6 klux [32]. The higher optimal light intensity, from 6 to 8.37 klux, found in this study may be due to a shading effect of LAB and PNSB in the fermentation broth. Hence, higher light intensity is needed for hydrogen fermentation by bioaugmentation system than that by PNSB alone.Fig. 3

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