Kinetic Study on the Effect of Substrate and Micronutrient Inhibition during Anaerobic Fermentation of Biohydrogen

There are several factors that influence the production of biohydrogen by dark fermentation including inoculum seeds, type and concentration of substrate, pH, temperature, presence of micronutrient and reactor configuration. Previous research has proven that the concentration of substrate and the presence of micronutrient will influence the yield and productivity of biohydrogen production. However, improvement of yield and productivity of the process can only be achieved once the system is under the optimum amount of substrate and micronutrient. Therefore, the best way to determine the effect of substrate concentration and presence of micronutrient is through kinetic study that was done using Monod model along with Andrews model. Besides that, the substrate inhibition effect also will be evaluated to determine the maximum substrate that needs to be supplied for maximum hydrogen production, and thus supplied the information for economic feasibility for fermentation process. In the meantime, the inhibition effect of adding the iron nanoparticles also had been evaluated in order to understand the interaction effect between iron nanoparticles and bacteria in term of catabolism reaction. It was found that increasing the substrate concentration more than 10 g/l will cause the inhibition to the system, in which it will slow down the reaction process and reduced the production of hydrogen. While the presence of iron NPs more than its optimum value (200 mg/l) will inhibit the bacterial growth and hence, affect the hydrogen production. For both cases, when the inhibition occurred at the respective concentration, it was found that the metabolic pathway was shifted to produce more hydrogen-consuming metabolite such as propionate acid, and thus, dropped the hydrogen production.

Anaerobic Co-Digestion of Oil Palm Frond Waste with Cow Manure for Biogas Production: Influence of a Stepwise Organic Loading on the Methane Productivity)

Anaerobic co-digestion of oil palm frond waste with cow-manure was evaluated. The study aimed to evaluate a stepwise organic load with an increase solid concentration to the on-going anaerobic digestion of cow manure. The anaerobic digestion process was operated in continuous mode under the mesophilic condition. Results showed that the maximum methane productivity of 1700 ml CH4∙day-1 was obtained when the anaerobic co-digestion of OPFW and cow manure was loaded with the substrate concentration between 4 and 8% TS. The pH culture dropped dramatically from 6.9 to 6.3 when substrate concentration was increased from 10 to 12% TS. The acidic pH had restricted the conversion of organic materials in which the COD removal was less than 25% removal. This study is exceedingly notable for the industrial development of waste management processes, which handle and treat tons of organic wastes daily.

MODEL ESTIMASI BIOKINETIKA UNTUK PROSES POST-DENITRIFIKASI AIR LIMBAH DOMESTIK PADA UNIT ANAEROBIC BAFFLED REACTOR

This study developed a combination of Continuous Stirred Tank Reactor (CSTR) for the acid fermentation and the Anaerobic Baffled Reactor (ABR) post-denitrification through high nitrite injection. Volatile Fatty Acids (VFAs) as a substrate for the post-denitrification process were optimally produced in the acid fermentation process. The aim of this study was to obtain the estimation of biokinetic values to predict the effluent wastewater quality in ABR post-denitrification process under unsteady state. The reactor was operated for HRT 7 days at temperature 25-28 ˚C and pH 6-7,2. The influent and effluent substrate concentration were monitored continuously for 160 days. Post-denitrification biokinetic from the Contois equation resulted in the value of hydrolysis rate (Kh) of 0.077 day-1, the substrate transport rate (k) of 4.364×10-6 Lmg-1day-1, maximum specific growth rate (μmax) of 0.559 day-1, half saturation constant (KS) of 0.209 mgL-1, microbial decay coefficient (b) of 0.0145 days-1; yield coefficient (Y) of 0.084 g-VSSg-COD-1. The validation of biokinetic parameters based on statistical analysis showed fairly precise results following the trend of experimental data to determine the substrate concentration in the effluent unit. Therefore, the biokinetic values can be applied in the design of ABR post-denitrification using primary sludge incorporation with high strength nitrate.Keywords: Anaerobic baffled reactor, biokinetics, Contois, hydrolysis, post-denitrification.

Mathematical Modelling of Canola Oil Biodegradation and Optimisation of Biosurfactant Production by an Antarctic Bacterial Consortium Using Response Surface Methodology

An Antarctic soil bacterial consortium (reference BS14) was confirmed to biodegrade canola oil, and kinetic studies on this biodegradation were carried out. The purpose of this study was to examine the ability of BS14 to produce biosurfactants during the biodegradation of canola oil. Secondary mathematical equations were chosen for kinetic analyses (Monod, Haldane, Teissier–Edwards, Aiba and Yano models). At the same time, biosurfactant production was confirmed through a preliminary screening test and further optimised using response surface methodology (RSM). Mathematical modelling demonstrated that the best-fitting model was the Haldane model for both waste (WCO) and pure canola oil (PCO) degradation. Kinetic parameters including the maximum degradation rate (μmax) and maximum concentration of substrate tolerated (Sm) were obtained. For WCO degradation these were 0.365 min−1 and 0.308%, respectively, while for PCO they were 0.307 min−1 and 0.591%, respectively. The results of all preliminary screenings for biosurfactants were positive. BS14 was able to produce biosurfactant concentrations of up to 13.44 and 14.06 mg/mL in the presence of WCO and PCO, respectively, after optimisation. The optimum values for each factor were determined using a three-dimensional contour plot generated in a central composite design, where a combination of 0.06% salinity, pH 7.30 and 1.55% initial substrate concentration led to the highest biosurfactant production when using WCO. Using PCO, the highest biosurfactant yield was obtained at 0.13% salinity, pH 7.30 and 1.25% initial substrate concentration. This study could help inform the development of large-scale bioremediation applications, not only for the degradation of canola oil but also of other hydrocarbons in the Antarctic by utilising the biosurfactants produced by BS14.

Effect of the Influent Substrate Concentration on Nitrogen Removal from Summer to Winter in Field Pilot-Scale Multistage Constructed Wetland–Pond Systems for Treating Low-C/N River Water

The quality of micropolluted water is unstable and its substrate concentration fluctuates greatly. The goal is to predict the concentration effect on the treatment of nitrogen in a river with an actual low C/N ratio for the proposed full-scale Xiaoyi River estuary wetland, so that the wetland project can operate stably and perform the water purification function effectively in the long term. Two pilot-scale multistage constructed wetland–pond (MCWP) systems (S1 and S2, respectively) based on actual engineering with the same “front ecological oxidation ponds, two-stage horizontal subsurface flow constructed wetlands and surface flow constructed wetlands (SFCWs) as the core and postsubmerged plant ponds” as the planned process were constructed to investigate the effect of different influent permanganate indexes (CODMn) and total nitrogen (TN) contents on nitrogen removal from micropolluted river water with a fixed C/N ratio from summer to winter in the field. The results indicate that the TN removal rate in the S1 and S2 systems was significant (19.56% and 34.84%, respectively). During the process of treating this micropolluted water with a fixed C/N ratio, the influent of S2 with a higher CODMn concentration was conducive to the removal of TN. The TN removal rate in S2 was significantly affected by the daily highest temperature. There was significant nitrogen removal efficiency in the SFCWs. The C/N ratio was a major determinant influencing the nitrogen removal rate in the SFCWs. The organic matter release phenomenon in SFCWs with high-density planting played an essential role in alleviating the lack of carbon sources in the influent. This research strongly supports the rule that there is seasonal nitrogen removal in the MCWPs under different influent substrate concentrations, which is of guiding significance for practical engineering.

Efficient production of isomaltose and isomaltooligosaccharides from starch using 1,4-α-glucan 6-α-glucosyltransferase and isopullulanase

We attempted to develop an efficient method for producing isomaltose, a disaccharide consisting of an α-(1→6)-linkage, from starch by combining enzymes of known activity. We found that the combination of 1,4-α-glucan 6-α-glucosyltransferase from Bacillus globisporus N75 and isopullulanase from Aspergillus brasiliensis ATCC 9642 led to the efficient synthesis of isomaltose. Inclusion of isoamylase and cyclomaltodextrin glucanotransferase resulted in increased efficiency, with production yields exceeding 70%. Furthermore, we considered that isomaltooligosaccharides could be synthesized from starch by combining 1,4-α-glucan 6-α-glucosyltransferase from Paenibacillus sp. PP710 and isopullulanase. In reactions that additionally utilized isoamylase and α-amylase, the total concentration of product, which included a series of isomaltooligosaccharides from isomaltose to isomaltodecaose, was 131 mM, and the ratio of 6-linked glucopyranosyl bonds to all bonds was 91.7% at a substrate concentration of 10%. The development of these manufacturing methods will accelerate the industrial production of isomaltose and isomaltooligosaccharides.

Production of gluconic acid by fungal species isolated from soil in Keffi, Nigeria

This investigation aimed at production of gluconic acid by fungal species isolated from soil in Keffi. Standard microbiological methods were employed for isolation and identification of the fungal isolates. The yields of gluconic acid produced by the different isolates of the fungi were determined using gas chromatograph and mass Spectrometry. The occurrence of fungi showed that Rhizopus oryzae was 100%, Aspergillus carneus was 75.0%, Aspergillus niger was 75.0% and Aspergillus terreus was 100% while Trichoderma viride was 25.0% and Fusarium moniliforme was 25.0%. The result further demonstrated that three species of the fungal isolates Aspergillus niger, Aspergillus carneus and Fusarium moniliforme were found to produce gluconic acid. Screening for gluconic acid production showed that Aspergillus carneus isolated from locations As1, Cs1 and Cs2, Aspergillus niger isolated from locations Bs1, Bs2 and Cs4 were able to produce gluconic acid. Result of effect of temperature, pH, substrate concentration and fermentation time on production of gluconic acid showed that Aspergillus niger Bs2 produced highest amount of gluconic acid at 28oC, similarly highest amount for gluconic acid produced by Aspergillus carneus As1 was at 28oC, whereas Fusarium moniliforme Bs4 produced highest at 30OC. pH 6.5 was found to the best optima pH for production of both gluconic acid for the fungi studied namely Aspergillus niger Bs2 and Aspergillus carneus As1 and Fusarium moniliforme Bs4 produced highest gluconic acid at pH 5.5. The substrate concentration showed highest production of gluconic acid was produced by Aspergillus niger Bs2 at substrate concentration of 25%. Aspergillus carneus As1 produced highest at substrate concentration of 20% and Fusarium moniliforme Bs4 produced highest at substrate concentration of 20%. The fermentation time showed highest production of gluconic acid by Aspergillus niger Bs2 and Aspergillus carneus As1 was after 144 hours whereas F. moniliforme Bs4 produced gluconic acid after 120hrs respectively. The fungi species isolated from soil in keffi revealed great ability in production of gluconic acid.