Roshanida A. Rahman

Optimization of process parameters for pilot-scale liquid-state bioconversion of sewage sludge by mixed fungal inoculation

Liquid-state bioconversion (LSB) technique has great potential for application in bioremediation of sewage sludge. The purpose of this study is to determine the optimum level of LSB process of sewage sludge treatment by mixed fungal (Aspergillus niger and Penicillium corylophilum) inoculation in a pilot-scale bioreactor. The optimization of process factors was investigated using response surface methodology based on Box–Behnken design considering hydraulic retention time (HRT) and substrate influent concentration (S0) on nine responses for optimizing and fitted to the regression model. The optimum region was successfully depicted by optimized conditions, which was identified as the best fit for convenient multiple responses. The results from process verification were in close agreement with those obtained through predictions. Considering five runs of different conditions of HRT (low, medium and high 3.62, 6.13 and 8.27 days, respectively) with the range of S0 value (the highest 12.56 and the lowest 7.85u2005gu2005L−1), it was monitored as the lower HRT was considered as the best option because it required minimum days of treatment than the others with influent concentration around 10u2005gu2005L−1. Therefore, optimum process factors of 3.62 days for HRT and 10.12u2005gu2005L−1 for S0 were identified as the best fit for LSB process and its performance was deviated by less than 5% in most of the cases compared to the predicted values. The recorded optimized results address a dynamic development in commercial-scale biological treatment of wastewater for safe and environment-friendly disposal in near future.

Assessment of sewage sludge bioremediation at different hydraulic retention times using mixed fungal inoculation by liquid-state bioconversion

Sustainable, environmental friendly, and safe disposal of sewage treatment plant (STP) sludge is a global expectation. Bioremediation performance was examined at different hydraulic retention times (HRT) in 3–10xa0days and organic loading rates (OLR) at 0.66–7.81xa0g chemical oxygen demand (COD) per liter per day, with mixed filamentous fungal (Aspergillus niger and Penicillium corylophilum) inoculation by liquid-state bioconversion (LSB) technique as a continuous process in large-scale bioreactor. Encouraging results were monitored in treated sludge by LSB continuous process. The highest removal of total suspended solid (TSS), turbidity, and COD were achieved at 98, 99, and 93xa0%, respectively, at 10xa0days HRT compared to control. The minimum volatile suspended solid/suspended solid implies the quality of water, which was recorded 0.59 at 10xa0days and 0.72 at 3xa0days of HRT. In treated supernatant with 88xa0% protein removal at 10xa0days of HRT indicates a higher magnitude of purification of treated sludge. The specific resistance to filtration (SRF) quantifies the performance of dewaterability; it was recorded minimum 0.049 × 1012xa0mxa0kg−1 at 10xa0days of HRT, which was equivalent to 97xa0% decrease of SRF. The lower OLR and higher HRT directly influenced the bioremediation and dewaterability of STP sludge in LSB process. The obtained findings imply encouraging message in continuing treatment of STP sludge, i.e., bioremediation of wastewater for environmental friendly disposal in near future.

Development and validation of a medium for recombinant endo-β-1,4-xylanase production by Kluyveromyces lactis using a statistical experimental design

Kluyveromyces lactis is an excellent host for a high cell density culture, which allows high expression levels of recombinant enzymes. Nutrient composition and culture conditions affect the secretion, production level and stability of the recombinant host. Therefore, it is technologically important to formulate a medium that stimulates high cell density and enhances the desired enzyme production using K. lactis GG799. In this study, six media were initially compared, and a Plackett-Burman experimental design was employed to screen for important components and trace elements. Nitrogen sources such as ammonium sulfate and free amino acid (casamino acid) as well as compounds like MgSO4∙7H2O, Na2SO4, ZnSO4∙6H2O, MnSO4∙4H2O and KH2PO4 affected biomass concentrations (5.67xa0g/l) and recombinant endo-β-1,4-xylanase (Xyn2) production (49.73 U/ml). Optimum productivity was obtained at shorter incubation times (i.e., 6xa0h), making the medium suitable for use when seeking efficient production. Expression of recombinant Xyn2 by K. lactis GG799 in the designed medium resulted in satisfactory recombinant Xyn2 volumetric productivity (vp) at 8.29 U/ml/h. When compared to the rich, non-selective YPD medium, the designed medium improved biomass output and recombinant Xyn2 production in K. lactis GG799 by approximately 9 and 22%, respectively.

Optimization of fresh palm oil mill effluent biodegradation with Aspergillus niger and Trichoderma virens

Abstract In this work, response surface optimization strategy was employed to enhance the biodegradation process of fresh palm oil mill effluent (POME) by Aspergillus niger and Trichoderma virens. A central composite design (CCD) combined with response surface methodology (RSM) were employed to study the effects of three independent variables: inoculum size (%), agitation rate (rpm) and temperature (°C) on the biodegradation processes and production of biosolids enriched with fungal biomass protein. The results achieved using A. niger were compared to those obtained using T. virens. The optimal conditions for the biodegradation processes in terms of total suspended solids (TSS), turbidity, chemical oxygen demand (COD), specific resistance to filtration (SRF) and production of biosolids enriched with fungal biomass protein in fresh POME treated with A. niger and T. virens have been predicted by multiple response optimization and verified experimentally at 19% (v/v) inoculum size, 100 rpm, 30.2°C and 5% (v/v) inoculum size, 100 rpm, 33.3°C respectively. As disclosed by ANOVA and response surface plots, the effects of inoculum size and agitation rate on fresh POME treatment process by both fungal strains were significant.

Synthesis and Application of Carbon Cryogel Beads Using Coconut Husk for Dye Removal

The production cost of carbon cryogels has been reduced by using alternative starting materials as precursor such as wattle tannin and furfural. In this study, a novel carbon cryogel beads were synthesized from low cost and abundant agricultural waste, coconut husk. Lignin was extracted and the percentages of lignin yield and lignin degradation were 27.63% and 13.39wt% respectively which were considered low due to the low operating temperature of lignin extraction in this study. The lignin extracted was then mixed with formaldehyde, sodium hydroxide, ethanol, and distilled water to undergo sol-gel polycondensation, followed by freeze drying and pyrolysis in an inert atmosphere to produce carbon cryogel beads. The adsorption of methyl blue on carbon cryogel beads increased with increasing with pH, initial dye concentration and temperature.

Evaluation of knowledge, attitude and practices of food handlers in campus cafeterias

The aim of this study is to assess the knowledge, attitude and practices (KAP) of food safety among food handlers of cafeterias in a university campus. It is a common scenario for university students in Malaysia to have their meals in cafeterias within the campus area. In a normal academic semester session, the number of students in the campus can be thousands at one time. The issue of hygienic level in cafeterias in universities is alarming since the number of students in a university campus is much higher than in a school. In general, food handlers should pay serious attention towards food hygiene and safety in order to avoid foodborne disease. It is highly critical to investigate thoroughly the hygienic level in the cafeterias inside the campus so that to totally understand the level of risk students are exposed to when having their meals in the cafeterias. To get such information is fundamental in strategising means to ensure the level of hygiene in the cafeterias is at least, acceptable for non-harmful effects to the students. This has motivated the design and execution of this study. In this study, all cafeterias in a selected university campus located in Peninsular Malaysia were evaluated for their level of hygiene. There was a total of 30 cafeteria’s food handlers altogether included in the investigation. The KAP level was assessed by giving out properly designed questionnaires to the food handlers. It is important for food handlers to equip themselves with knowledge on good food handling practices. Beside knowledge and law enforcement, the attitude of the food handlers also is another important factor that may influence the occurrence of foodborne disease. Basically, all three traits; knowledge, attitude and education, are compulsory to achieve safe food handling practice. Therefore all these three aspects were taken into account in details in this study. Based on the findings, correlations between these aspects were established. Besides, appropriate recommendations to overcome the problems revealed from this study are also provided.

Microbial growth kinetics in isobutanol production by saccharomyces cerevisiae

Renewable sources of fuels are important for environmental sustainability. Biofuels are produced from renewable feedstocks through biological processes and can be found in the form of liquid, gas and solid. Isobutanol, a branched chain butanol isomer, is a type of biofuel that can be produced through the fermentation of biomass using microorganisms. In an aerobic fermentation, Saccharomyces cerevisiae (yeast) produced certain amount of isobutanol as by-product during the degradation of valine through the Ehrlich pathway. In the fermentation process, the determination of growth kinetics gives a better explanation regarding the relationship between specific growth rate and the concentration of a substrate. Kinetic coefficients are useful in providing information regarding the progression of either the chemical or biological reaction occurring in a system. In this study, the microbial growth kinetics, glucose utilisation and isobutanol productivity were investigated. The growth kinetics coefficients were determined by the Monods model while the Ledeuking-Pirets model were used in investigating the parameters involved in substrates consumption and products formation. The maximum specific growth rate, μmax and the substrate saturation constant, Ks were determined from the slope and interception point (a plot between 1/μ and 1/S) during 48 h of fermentation period. The value of μmax and Ks obtained were 0.74 h-1 and 57 g/L. The isobutanol yield (YP/S), biomass yield (YX/S) and the correlation between isobutanol production and yeast growth (YP/X) were found to be 4.79 mg/g, 0.1 g/g and 49.4 mg/g. The Monods and Leudeking-Pirets models were found to be suitable to represent the experimental data of growth kinetics and products formation kinetics in this study.

Optimisation of Fermentation Conditions for Isobutanol Production by Saccharomyces Cerevisiae Using Response Surface Methodology

Alternative fuels from renewable sources are receiving public and scientific attention due to continuous depletion of petroleum fuel-reserves and environmental problem such as global warming and climate change. Transportation fuel from biofuel is extensively encouraged as it is known to be both renewable and environmentally friendly source of energy. Isobutanol is one of the suitable candidates in replacing gasoline as transportation fuel. This fuel is superior compared to the biofuel that have been commercialised, bioethanol, as it possesses several advantages including high energy content, low solubility, and has lower vapour pressure. Yeast Saccharomyces cerevisiae is able to produce small amount of isobutanol naturally as the end product of amino acid degradation. In order to increase the isobutanol production, experiments based on response surface methodology (RSM) with central composite design (CCD) were conducted to study the effects of operating conditions by Saccharomyces cerevisiae towards isobutanol yield. The independent variables studied were temperature (28-40 °C), pH (4-7), agitation speed (50-200 rpm), and inoculum size (3-10% v/v). From the experimental results, maximum isobutanol concentration of 200 mg/L was obtained at the optimum condition of temperature (28 °C), pH (7), agitation speed (179 rpm), and inoculum size (10 % v/v). The experimental value (200 mg/L) agreed well with the predicted value from mathematical model (220 mg/L), indicates the suitability of the model and the success of response surface methodology in optimising the operating conditions of isobutanol production. Throughout the study, it can be concluded that the isobutanol yield can be increased by manipulating several factors.

New Advancement on Cross-Linked Enzyme Aggregates within Magnetically-Separable Mesoporous Silica

Magnetically-separable enzyme system has been developed by adsorption, precipitation and cross-linking of enzymes in superparamagnetic hierarchically ordered mesoporous mesocellular silica (M-HMMS). The immobilization of xylanase within M-HMMS were compared between enzyme adsorption (EA), enzyme adsorption and cross-linking (EAC), and enzyme adsorption, precipitation and cross-linking (EAPC). EAPC includes higher enzyme activity immobilized within the matrix in comparison with the other methods. Furthermore, the immobilized enzyme is predicted to be prevented from leaching out of the matrix when exterior blow is being tested on the structure. Thus, the stability of the EAPC of this invention is anticipated to be maintained even after a long time passed since high enzyme activity compared with known method can be supported and immobilized within the matrix. Consequently, it is possible to improve performance of the enzymes by manipulating the preparation and operation condition.

Preparation and Characterization of Textile Sludge-Based Activated Carbon for Dyes Removal

An activated carbon derived from textile sludge was synthesized as an initiative of low cost adsorbent for removal of dyes. The surface area of this activated carbon was determined by Brunauer, Emmett and Teller (BET). From the BET results, it shows a high increment in the BET multi point area for textile sludge-activated carbon as compared to the textile sludge, which is 623.9557 m2/g and 58.9806 m2/g, respectively. The effects of initial adsorbent dosage were studied in the removal of Reactive Black 5 (RB5) and Methylene Blue (MB) dyes. RB5 and MB dyes solutions were used to represent anionic and cationic dyes respectively. It was concluded that the adsorbent dosage was proportional to the dyes removal for both RB5 and MB with percentage removal up to 99%.