Physicochemical characteristics of attached biofilm on granular activated carbon for thermophilic biohydrogen production

Abstract

In this study, thermophilic biohydrogen production by a mixed culture, obtained from a continuous acidogenic reactor treating palm oil mill effluent, was improved by using granular activated carbon (GAC) as the support material. Batch experiments were carried out at 60 C by feeding the anaerobic sludge bacteria with a sucrose-containing synthetic medium at an initial pH of 5.5 under anoxic conditions. The physico-chemical characteristics of the attached biofilm were evaluated after extraction of the extracellular polymeric substances (EPSs) of the biofilm using the formaldehyde-NaOH method. The main component of the biofilm was protein (60%), while the carbohydrate content accounted for 40% of the EPS. Two major absorption bands at approximately 3400 cm À1 and 1650 cm À1 , characteristics of the stretching vibrations of hydroxyl and amino groups, respectively, were identified in the FT-IR spectra, confirming the composition of the EPS. Observations using scanning electron microscopy (SEM) illustrated the attachment of rod-shaped bacterial cells on the GAC at 60 C. A maximum hydrogen production rate of 4.3 mmol L À1 h À1 and a hydrogen yield of 5.6 mol H 2 per mol sucrose were obtained from this attached biofilm system. The major soluble metabolites of fermentation were acetic acid and butyric acid. The results showed that the granular activated carbon enhanced the biohydrogen production by stabilizing the pH and microbial metabolites and therefore could be used as a support material for fermentative hydrogen production under thermophilic conditions on a large scale. Fig. 2 Batch kinetics of hydrogen production from sucrose with GAC-attached biofilm at 60 C and initial pH of 5.5. (a) Gompertz curve-fitting graph of cumulative gas production and (b) composition of soluble metabolites (acetic acid -HAc, butyric acid -HBu and ethanol -EtOH) and sugar consumption.19386 | RSC Adv., 2015,5,[19382][19383][19384][19385][19386][19387][19388][19389][19390][19391][19392] This journal is

Biofilm formation on granular activated carbon in xylose and glucose mixture for thermophilic biohydrogen production

“…Meanwhile, the trends of hydrogen yield and the HPR obtained (Table 3) were comparable among other runs that contained GAC at different ratio of B, C, E and F. There is not much different in term of hydrogen yield under different i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y x x x ( 2 0 1 6 ) 1 e1 1 loading of GAC, that is when results of run B and C is compared to D. It can be said that the porous structure and irregular space present on the surface of the carrier provided an adequate space for the sludge to grow well as in agreement in the results obtained by Lutpi et al [45]. The trends, however, decrease when further increase of added GAC in run E and F which shows that the microbial population of the sludge have some limitation to grow in the surrounding of large amount of support carrier in a batch fermentation.…”

“…5 (d) illustrates the attachment of microbial sludge was successfully developed and filled the cavities of GAC. The same attachment behavior was also observed by Lutpi et al [45], in their work using synthetic media containing sucrose. It is clearly noticeable that several layers of cell had adhered on the porous surface of GAC, forming a stable biofilm that is believed as a result of the cell growth on glucose and xylose during the fermentation.…”

“…The attachment formed biofilm helped sustaining cell viability and which would prevent the cells washout from the system, thereby enhanced culture density. The surface porosity of the GAC eased the sludge to attach on the carrier surface and forming a stable biofilm [45], likewise, a consistent biohydrogen production was also obtained in the system. The results also illustrated that the acclimatization process has i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y x x x ( 2 0 1 6 ) 1 e1 1 advocated the cell density to adhere on the GAC surface, thereby provided consistent and stable hydrogen production at thermophilic condition as in agreement with Zhang et al, [46].…”

Potential use of coconut shell activated carbon as an immobilisation carrier for high conversion of succinic acid from oil palm frond hydrolysate

“…The surface area and pore characteristics of materials determine the extent of adhesion (i.e., cell-surface interaction) and cohesion (i.e., cell-cell interaction). 41 As shown in Table 2, both coconut shell and coal activated carbon materials had much higher specic surface area and total pore volume, compared to other materials. It is worthy of note that larger pore volume implies higher capacity to hold a substance of interest.…”

“…19,45 Typically, the main components in EPSs are proteins and polysaccharides which facilitate in the overall binding process. 41 Hence, the composition of the EPS fraction of A. succinogenes on different carrier materials is tabulated in Table 3. It was found that proteins are a predominant constituent in the EPSs.…”