scholarly journals Enhancement of biohydrogen production from the aquatic weed Pistia stratiotes through a dark fermentation process

2019 ◽  
Author(s):  
◽  
Nonsikelelo Precios Mthethwa
Keyword(s):  
Hydrogen Production ◽  
Fermentation Process ◽  
Dark Fermentation ◽  
Biohydrogen Production ◽  
Pistia Stratiotes ◽  
Aquatic Weed ◽  
Operational Conditions ◽  
Bacillus Spp ◽  
Pre Treatment ◽  
Clostridium Spp

Aquatic weeds are well known for their fast growth rate and high carbohydrate content that can be easily hydrolysed into fermentable sugars. This study was aimed at the utilization of an indigenous aquatic weed, Pistia stratiotes for biohydrogen production through the dark fermentation process. Characterization of the biomass, effect of pre–treatment methods on biomass hydrolysis, effect of reactor operational conditions and type of inoculum on enhancing hydrogen production potential of P. stratiotes was assessed. Physical and chemical pre–treatments were employed on P. stratiotes biomass to increase digestibility and to achieve high conversion rates of fermentable sugars. The highest sugar yield of 139± 0.8 mg/g was obtained when the oven dried biomass was subjected to H2SO4 (2.5%) pre– treatment followed by autoclaving at 121°C for 30 min. Biohydrogen production under different operational conditions was thereafter optimized using One–factor–at–a–time (OFAT) batch experiments in 120 mL serum bottles. A maximum hydrogen yield (HY) of 2.46 ± 0.14 mol-H2/mol-glucose (3.51 ± 0.20 mg-H2/g-dry weight) and 2.75 ± 0.07 mL h-1 hydrogen production rate was observed under optimized conditions (pH 5.5, Temp 35°C, S/X: 1.0 g-COD/g-VSS and HRT 8 h). The organic mass balance (92 – 96%) and electron– equivalent balance (92 – 98%) further indicated the reliability of the obtained fermentation data. Assessment of microbial activity was achieved using molecular techniques such as quantitative polymerase chain reaction (qPCR) targeting both 16s rRNA (of Clostridium spp., Bacillus spp., and Enterobacter spp.) and the functional hydrogenase gene (hydA). The highest gene activity of hydrogenase was noted at pH of 5.5 with 2.53×104 copies/ng-DNA compared to low pH: 4.5 (6.95 × 103 copies/ng-DNA) and high pH: 8.5 (7.77×103 copies/ng- DNA). A similar trend was also observed for the species containing a highly active hydrogenase (i.e. Clostridium spp., Bacillus spp., and Enterobacter spp.). During the optimum reactor conditions, three hydrogen producing bacterial strains Bacillus cereus and Enterobacter cloacae were successfully isolated. These isolates were used as inoculums for the pure culture studies and achieved HYs of 2.2, 1.10 and 1.97 mol-H2/mol-glucose respectively under optimized fermentation conditions. However, the thermally treated mixed culture displayed a marginally higher HY (2.46 mol-H2/mol-glucose) compared to the pure culture used alone. Furthermore, the cost estimation indicated a potential and economically feasible for biotransformation of P. stratiotes to hydrogen energy. In conclusion, the results from this study has revealed the potential of employing P. stratiotes biomass for biohydrogen production. The results also indicated the importance of employing suitable pre–treatment methods, operating conditions as well as inoculum types for enhanced hydrogen production using P. stratiotes.

scholarly journals Evaluation of biohydrogen production potential of sugarcane bagasse using activated sludge in a dark fermentation process

2016 ◽  
Author(s):  
◽  
Karen Reddy
Keyword(s):  
South Africa ◽  
Sewage Sludge ◽  
Hydrogen Production ◽  
Activated Sludge ◽  
Sugarcane Bagasse ◽  
Magnetite Nanoparticles ◽  
Fermentation Process ◽  
Dark Fermentation ◽  
Hydrogenase Gene ◽  
Pre Treatment

Anaerobic dark fermentation is an efficient biological process to produce hydrogen from waste material. In South Africa, this technology has not been explored adequately to extract energy from biological wastes. Within the KwaZulu Natal region of South Africa, the sugar industry is a prominent venture that produces mass quantities of sugarcane bagasse amongst other waste products. This by-product can be an ideal source of substrate for biohydrogen generation. In this study, sugarcane bagasse was used as the main substrate for biohydrogen production by anaerobic fermentation using sewage sludge as the inoculum. Different pre-treatment methods were employed to maximize the release of fermentable sugars from the lignocellulosic biomass. Among the different pre-treatment methods employed, the maximum sugar yield (294.4 mg/g) was achieved with 0.25% H2SO4 for 60 minutes at 121°C. Prior to inoculation, the sewage sludge was also subjected to thermal pre-treatment to eliminate methanogens. Thermal pre-treatment of inoculum sludge for 30 min was effective in eliminating methanogens. Fluorescence in situ hybridization was used to positively identify the hydrogen producing bacteria present before and after treatment. The pre-treated substrate and inoculum was integrated into a dark fermentation process to further optimize the effect of pH, substrate to biomass, iron and magnetite nanoparticles on hydrogen production. The maximum hydrogen production (1.2 mol/mol glucose) was achieved at a pH range of 5-6, a substrate to biomass ratio of 3.5, and iron and magnetite nanoparticle concentration of 200 mg/L. Microbial analysis using quantitative polymerase chain reaction has confirmed the dominance of Clostridium spp. in the reactor. The highest hydrogenase gene activity (number of copies of hydrogenase gene expression/ng DNA) was recorded in the reactor supplemented with magnetite nanoparticles with lowest being in the raw sludge. There was a direct positive correlation between the hydrogenase gene copy number and the hydrogen yield obtained at different reactor conditions. Scanning electron microscopy was a useful to visually analyse the interaction of microorganisms with activated sludge. This study highlights the significance of anaerobic microorganisms from waste sludge being able to utilize agricultural waste material to produce biohydrogen which could be further scaled up for continuous hydrogen production. In addition, statistical tools used to predict the possible sugar (Design of experiments) and hydrogen yields (Gompertz model) produced would be helpful in saving time during full-scale operation of biohydrogen producing reactors.

scholarly journals Zeolite addition to improve biohydrogen production from dark fermentation of C5/C6-sugars and Sargassum sp. biomass

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
R. M. Silva ◽  
A. A. Abreu ◽  
A. F. Salvador ◽  
M. M. Alves ◽  
I. C. Neves ◽  
...  
Keyword(s):  
Hydrogen Production ◽  
Anaerobic Bacteria ◽  
Dark Fermentation ◽  
Inorganic Materials ◽  
Biohydrogen Production ◽  
High Rate ◽  
Continuous Reactor ◽  
Organic Loading Rate ◽  
Fermentation Products ◽  
Zeolite Type

AbstractThermophilic biohydrogen production by dark fermentation from a mixture (1:1) of C5 (arabinose) and C6 (glucose) sugars, present in lignocellulosic hydrolysates, and from Sargassum sp. biomass, is studied in this work in batch assays and also in a continuous reactor experiment. Pursuing the interest of studying interactions between inorganic materials (adsorbents, conductive and others) and anaerobic bacteria, the biological processes were amended with variable amounts of a zeolite type-13X in the range of zeolite/inoculum (in VS) ratios (Z/I) of 0.065–0.26 g g−1. In the batch assays, the presence of the zeolite was beneficial to increase the hydrogen titer by 15–21% with C5 and C6-sugars as compared to the control, and an increase of 27% was observed in the batch fermentation of Sargassum sp. Hydrogen yields also increased by 10–26% with sugars in the presence of the zeolite. The rate of hydrogen production increased linearly with the Z/I ratios in the experiments with C5 and C6-sugars. In the batch assay with Sargassum sp., there was an optimum value of Z/I of 0.13 g g−1 where the H2 production rate observed was the highest, although all values were in a narrow range between 3.21 and 4.19 mmol L−1 day−1. The positive effect of the zeolite was also observed in a continuous high-rate reactor fed with C5 and C6-sugars. The increase of the organic loading rate (OLR) from 8.8 to 17.6 kg m−3 day−1 of COD led to lower hydrogen production rates but, upon zeolite addition (0.26 g g−1 VS inoculum), the hydrogen production increased significantly from 143 to 413 mL L−1 day−1. Interestingly, the presence of zeolite in the continuous operation had a remarkable impact in the microbial community and in the profile of fermentation products. The effect of zeolite could be related to several properties, including the porous structure and the associated surface area available for bacterial adhesion, potential release of trace elements, ion-exchanger capacity or ability to adsorb different compounds (i.e. protons). The observations opens novel perspectives and will stimulate further research not only in biohydrogen production, but broadly in the field of interactions between bacteria and inorganic materials.

Enhanced bio-energy recovery in a two-stage hydrogen/methane fermentation process

2009 ◽  
Vol 59 (11) ◽  
pp. 2137-2143 ◽  
Author(s):  
M. J. Lee ◽  
J. H. Song ◽  
S. J. Hwang
Keyword(s):  
Hydrogen Production ◽  
Fermentation Process ◽  
Continuous Production ◽  
Strong Acid ◽  
Treatment Method ◽  
Engineering System ◽  
Production Rates ◽  
Two Stage ◽  
Methane Fermentation ◽  
Pre Treatment

A two-stage hydrogen/methane fermentation process has emerged as a feasible engineering system to recover bio-energy from wastewater. Hydrogen-producing bacteria (HPB) generate hydrogen from readily available carbohydrates, and organic acids produced during the hydrogen fermentation step can be degraded to generate methane in the following step. Three strong acids, HCl, H2SO4, and HNO3, were tested to determine the appropriate pre-treatment method for enhanced hydrogen production. The hydrogen production rates of 230, 290, and 20 L/kg-glucose/day was observed for the sludge treated with HCl, H2SO4, and HNO3, respectively, indicating that the acid pre-treatment using either HCl or H2SO4 resulted in a significant increase in hydrogen production. The fluorescent in situ hybridization method indicated that the acid pre-treatment selectively enriched HPB including Clostridium sp. of cluster I from inoculum sludge. After hydrogen fermentation was terminated, the sludge was introduced to a methane fermentation reactor. This experiment showed methane production rates of 100, 30, and 13 L/kg-glucose/day for the sludge pre-treated with HCl, H2SO4, and HNO3, respectively, implying that both sulfate and nitrate inhibited the activity of methane-producing bacteria. Consequently, the acid pre-treatment might be a feasible option to enhance biogas recovery in the two-stage fermentation process, and HCl was selected as the optimal strong acid for the enrichment of HPB and the continuous production of methane.

scholarly journals Optimization of Biohydrogen Production with Biomechatronics

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Shao-Yi Hsia ◽  
Yu-Tuan Chou
Keyword(s):  
Hydrogen Production ◽  
Taguchi Method ◽  
Alternative Energy ◽  
Production Efficiency ◽  
Biological Effects ◽  
Dark Fermentation ◽  
Operating Conditions ◽  
Biohydrogen Production ◽  
Process Conditions ◽  
Ultrasonic Frequency

Massive utilization of petroleum and natural gas caused fossil fuel shortages. Consequently, a large amount of carbon dioxide and other pollutants are produced and induced environmental impact. Hydrogen is considered a clean and alternative energy source. It contains relatively high amount of energy compared with other fuels and by-product is water. In this study, the combination of ultrasonic mechanical and biological effects is utilized to increase biohydrogen production from dark fermentation bacteria. The hydrogen production is affected by many process conditions. For obtaining the optimal result, experimental design is planned using the Taguchi Method. Four controlling factors, the ultrasonic frequency, energy, exposure time, and starch concentration, are considered to calculate the highest hydrogen production by the Taguchi Method. Under the best operating conditions, the biohydrogen production efficiency of dark fermentation increases by 19.11%. Results have shown that the combination of ultrasound and biological reactors for dark fermentation hydrogen production outperforms the traditional biohydrogen production method. The ultrasonic mechanical effects in this research always own different significances on biohydrogen production.

scholarly journals Thermophilic Dark Fermentation of Sewage Sludge for Biohydrogen Production - Influence of pH

2018 ◽  
Vol 20 (3) ◽  
pp. 564-571
Keyword(s):  
Sewage Sludge ◽  
Hydrogen Production ◽  
Waste Water Treatment ◽  
Dark Fermentation ◽  
Biohydrogen Production ◽  
Pure Hydrogen ◽  
Constant Ph ◽  
Initial Ph ◽  
Sludge Waste ◽  
Almost All

<p>This study investigates the usability of sewage sludge, waste from a waste water treatment facility, at the stable thermophilic temperature and different pH conditions in the biohydrogen production by dark fermentation. Without the addition of a pure hydrogen producer and nutrient source, the effect of a different constant pH in the range of pH 4-9 on biohydrogen production using sewage sludge was compared with that of a different initial pH. It was understood from the results that biohydrogen production varies according to the characterization of sewage sludge. In the experiments, the lag time was insignificant (~2h). The maximum hydrogen production was achieved at pH 5 within the first 24-30 hours of fermentation (92894 mL m-3 H2). Therefore, it was determined that the higher digestion efficiencies of the sewage sludge were obtained at pH 5. In general, with the increase in methanogens in the medium, the hydrogen producing ability and hydrogen content of the sewage sludge gradually decreased. Hydrogen production at almost all the pH values after the third day was less than 1000 mL m-3.</p>

scholarly journals Fermentative Conversion of Two-Step Pre-Treated Lignocellulosic Biomass to Hydrogen

Catalysts ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 858 ◽  
Author(s):  
Karolina Kucharska ◽  
Hubert Cieśliński ◽  
Piotr Rybarczyk ◽  
Edyta Słupek ◽  
Rafał Łukajtis ◽  
...  
Keyword(s):  
Hydrogen Production ◽  
Lignocellulosic Biomass ◽  
Lignin Content ◽  
Dark Fermentation ◽  
Biomass Composition ◽  
Total Phenolic ◽  
High Hydrogen ◽  
Fermentative Hydrogen Production ◽  
Pre Treatment ◽  
Fermentative Hydrogen

Fermentative hydrogen production via dark fermentation with the application of lignocellulosic biomass requires a multistep pre-treatment procedure, due to the complexed structure of the raw material. Hence, the comparison of the hydrogen productivity potential of different lignocellulosic materials (LCMs) in relation to the lignocellulosic biomass composition is often considered as an interesting field of research. In this study, several types of biomass, representing woods, cereals and grass were processed by means of mechanical pre-treatment and alkaline and enzymatic hydrolysis. Hydrolysates were used in fermentative hydrogen production via dark fermentation process with Enterobacter aerogenes (model organism). The differences in the hydrogen productivity regarding different materials hydrolysates were analyzed using chemometric methods with respect to a wide dataset collected throughout this study. Hydrogen formation, as expected, was positively correlated with glucose concentration and total reducing sugars amount (YTRS) in enzymatic hydrolysates of LCMs, and negatively correlated with concentrations of enzymatic inhibitors i.e., HMF, furfural and total phenolic compounds in alkaline-hydrolysates LCMs, respectively. Interestingly, high hydrogen productivity was positively correlated with lignin content in raw LCMs and smaller mass loss of LCM after pre-treatment step. Besides results of chemometric analysis, the presented data analysis seems to confirm that the structure and chemical composition of lignin and hemicellulose present in the lignocellulosic material is more important to design the process of its bioconversion than the proportion between the cellulose, hemicellulose and lignin content in this material. For analyzed LCMs we found remarkable higher potential of hydrogen production via bioconversion process of woods i.e., beech (24.01 mL H2/g biomass), energetic poplar (23.41 mL H2/g biomass) or energetic willow (25.44 mL H2/g biomass) than for cereals i.e., triticale (17.82 mL H2/g biomass) and corn (14.37 mL H2/g biomass) or for meadow grass (7.22 mL H2/g biomass).

scholarly journals Zeolite addition to improve biohydrogen production from dark fermentation of organic wastes

2020 ◽  
Author(s):  
Ana Rita M Silva ◽  
Angela A Abreu ◽  
Andreia F Salvador ◽  
Maria Madalena Alves ◽  
Isabel C Neves ◽  
...  
Keyword(s):  
Hydrogen Production ◽  
Microbial Community Composition ◽  
Dark Fermentation ◽  
Biohydrogen Production ◽  
Continuous Reactor ◽  
Batch Reactors ◽  
Biological Processes ◽  
Production Improvement ◽  
Volatile Solids ◽  
Zeolite Type

Abstract Background Hydrogen is a clean and renewable energy source that can be produced by biological processes, such as dark fermentation. However, hydrogen production yields are usually low.Results In this work, biohydrogen production from a mixture (1:1) of glucose and arabinose (4.4 g L -1 , in COD) was improved about 1.3 times in batch reactors, and increased 3 times in a continuous reactor (from 143 mL H2 L -1 d -1 to 430 mL H2 L -1 d -1 ), when zeolite type-13X was added. The presence of zeolite led to the stimulation of different metabolic pathways and to changes in the microbial community composition, which seems to be linked to hydrogen production improvement. The zeolite effect in dark fermentation was also verified for more complex substrates. Hydrogen production yield from Sargassum sp., was improved 1.4 times by the presence of zeolite (94.8 L H 2 Kg -1 Sargassum sp . Volatile Solids (VS)).Conclusions The results show that zeolite is suitable to improve biohydrogen production by dark fermentation.

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