Displaying publications 1 - 20 of 41 in total

  1. Rahim MHA, Hasan H, Harith HH, Abbas A
    Bioprocess Biosyst Eng, 2017 Dec;40(12):1753-1761.
    PMID: 28879627 DOI: 10.1007/s00449-017-1830-y
    This study investigates the effects of viscosity, friction, and sonication on the morphology and the production of lovastatin, (+)-geodin, and sulochrin by Aspergillus terreus ATCC 20542. Sodium alginate and gelatine were used to protect the fungal pellet from mechanical force by increasing the media viscosity. Sodium alginate stimulated the production of lovastatin by up to 329.0% and sulochrin by 128.7%, with inhibitory effect on (+)-geodin production at all concentrations used. However, the use of gelatine to increase viscosity significantly suppressed lovastatin, (+)-geodin, and sulochrin's production (maximum reduction at day 9 of 42.7, 60.8, and 68.3%, respectively), which indicated that the types of chemical play a major role in metabolite production. Higher viscosity increased both pellet biomass and size in all conditions. Friction significantly increased (+)-geodin's titre by 1527.5%, lovastatin by 511.1%, and sulochrin by 784.4% while reducing pellet biomass and size. Conversely, sonication produced disperse filamentous morphology with significantly lower metabolites. Sodium alginate-induced lovastatin and sulochrin production suggest that these metabolites are not affected by viscosity; rather, their production is affected by the specific action of certain chemicals. In contrast, low viscosity adversely affected (+)-geodin's production, while pellet disintegration can cause a significant production of (+)-geodin.
  2. Darah I, Sumathi G, Jain K, Lim SH
    Bioprocess Biosyst Eng, 2011 Sep;34(7):795-801.
    PMID: 21347668 DOI: 10.1007/s00449-011-0529-8
    The ability of immobilized cell cultures of Aspergillus niger FETL FT3 to produce extracellular tannase was investigated. The production of enzyme was increased by entrapping the fungus in scouring mesh cubes compared to free cells. Using optimized parameters of six scouring mesh cubes and inoculum size of 1 × 10(6) spores/mL, the tannase production of 3.98 U/mL was obtained from the immobilized cells compared to free cells (2.81 U/mL). It was about 41.64% increment. The immobilized cultures exhibited significant tannase production stability of two repeated runs.
  3. Serri NA, Kamaruddin AH, Long WS
    Bioprocess Biosyst Eng, 2006 Oct;29(4):253-60.
    PMID: 16868763
    Immobilized Candida rugosa lipase was used for the synthesis of citronellyl laurate from citronellol and lauric acid. Screening of different types of support (Amberlite MB-1 and Celite) for immobilization of lipase and solvent (n-hexane, n-heptane, and iso-octane) and optimization of reaction conditions, such as catalyst loading, effect of substrates molar ratio and temperature, have been studied. The maximum enzyme activity was obtained at 310 K. The immobilized C. rugosa lipase onto Amberlite MB-1 support was found to be the best support with a conversion of 89% of citronellyl laurate ester in iso-octane compared to Celite 545. Deactivation of C. rugosa lipase at 313, 318 and 323 K were observed. Ordered bi bi mechanism with dead end complex of lauric acid was found to fit the initial rate data and the kinetic parameters were obtained by non-linear regression analysis.
  4. Fuzi SF, Razali F, Jahim JM, Rahman RA, Illias RM
    Bioprocess Biosyst Eng, 2014 Sep;37(9):1887-98.
    PMID: 24633311 DOI: 10.1007/s00449-014-1163-z
    A xylanase gene (xyn2) from Trichoderma reesei ATCC 58350 was previously cloned and expressed in Kluyveromyces lactis GG799. The production of the recombinant xylanase was conducted in a developed medium with an optimised batch and with fed-batches that were processed with glucose. The glucose served as a carbon source for cell growth and as an inducer for xylanase production. In a 1-L batch system, a glucose concentration of 20 g L(-1) and 80 % dissolved oxygen were found to provide the best conditions for the tested ranges. A xylanase activity of 75.53 U mL(-1) was obtained. However, in the batch mode, glucose depletions reduced the synthesis of recombinant xylanase by K. lactis GG799. To maximise the production of xylanase, further optimisation was performed using exponential feeding. We investigated the effects of various nitrogen sources combined with the carbon to nitrogen (C/N) molar ratio on the production of xylanase. Of the various nitrogen sources, yeast extract was found to be the most useful for recombinant xylanase production. The highest xylanase production (110.13 U mL(-1)) was measured at a C/N ratio of 50.08. These conditions led to a 45.8 % increase in xylanase activity compared with the batch cultures. Interestingly, the further addition of 500 g L(-1) glucose led to a 6.2-fold increase (465.07 U mL(-1)) in recombinant xylanase activity. These findings, together with those of the exponential feeding strategy, indicate that the composition of the C/N molar ratio has a substantial impact on recombinant protein production in K. lactis.
  5. Adnan LA, Sathishkumar P, Yusoff AR, Hadibarata T, Ameen F
    Bioprocess Biosyst Eng, 2017 Jan;40(1):85-97.
    PMID: 27663440 DOI: 10.1007/s00449-016-1677-7
    In this study, a newly isolated ascomycete fungus Trichoderma lixii F21 was explored to bioremediate the polar [Alizarin Red S (ARS)] and non-polar [Quinizarine Green SS (QGSS)] anthraquinone dyes. The bioremediation of ARS and QGSS by T. lixii F21 was found to be 77.78 and 98.31 %, respectively, via biosorption and enzymatic processes within 7 days of incubation. The maximum biosorption (ARS = 33.7 % and QGSS = 74.7 %) and enzymatic biodegradation (ARS = 44.1 % and QGSS = 23.6 %) were observed at pH 4 and 27 °C in the presence of glucose and yeast extract. The laccase and catechol 1,2-dioxygenase produced by T. lixii F21 were involved in the molecular conversions of ARS and QGSS to phenolic and carboxylic acid compounds, without the formation of toxic aromatic amines. This study suggests that T. lixii F21 may be a good candidate for the bioremediation of industrial effluents contaminated with anthraquinone dyes.
  6. Zambry NS, Ayoib A, Md Noh NA, Yahya ARM
    Bioprocess Biosyst Eng, 2017 Jul;40(7):1007-1016.
    PMID: 28389850 DOI: 10.1007/s00449-017-1764-4
    The present study focused on developing a wild-type actinomycete isolate as a model for a non-pathogenic filamentous producer of biosurfactants. A total of 33 actinomycetes isolates were screened and their extracellular biosurfactants production was evaluated using olive oil as the main substrate. Out of 33 isolates, 32 showed positive results in the oil spreading technique (OST). All isolates showed good emulsification activity (E24) ranging from 84.1 to 95.8%. Based on OST and E24 values, isolate R1 was selected for further investigation in biosurfactant production in an agitated submerged fermentation. Phenotypic and genotypic analyses tentatively identified isolate R1 as a member of the Streptomyces genus. A submerged cultivation of Streptomyces sp. R1 was carried out in a 3-L stirred-tank bioreactor. The influence of impeller tip speed on volumetric oxygen transfer coefficient (k L a), growth, cell morphology and biosurfactant production was observed. It was found that the maximum biosurfactant production, indicated by the lowest surface tension measurement (40.5 ± 0.05 dynes/cm) was obtained at highest k L a value (50.94 h-1) regardless of agitation speed. The partially purified biosurfactant was obtained at a concentration of 7.19 g L-1, characterized as a lipopeptide biosurfactant and was found to be stable over a wide range of temperature (20-121 °C), pH (2-12) and salinity [5-20% (w/v) of NaCl].
  7. Sathishkumar P, Vennila K, Jayakumar R, Yusoff AR, Hadibarata T, Palvannan T
    Bioprocess Biosyst Eng, 2016 Apr;39(4):651-9.
    PMID: 26801668 DOI: 10.1007/s00449-016-1546-4
    In this study, phyto-synthesis of silver nanoparticles (AgNPs) was achieved using an aqueous leaf extract of Alternanthera tenella. The phytochemical screening results revealed that flavonoids are responsible for the AgNPs formation. The AgNPs were characterised using UV-visible spectrophotometer, field emission scanning microscopy/energy dispersive X-ray, transmission electron microscopy, fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction. The average size of the nanoparticles was found to be ≈48 nm. The EDX results show that strong signals were observed for the silver atoms. The strong band appearing at 1601-1595 cm(-1) correspond to C-C stretching vibration from dienes in FT-IR spectrum indicating the formation of AgNPs. Human breast adenocarcinoma (MCF-7) cells treated with various concentrations of AgNPs showed a dose-dependent increase in cell inhibition. The IC50 value of the AgNPs was calculated to be 42.5 μg mL(-1). The AgNPs showed a significant reduction in the migration of MCF-7 cells.
  8. Hadibarata T, Teh ZC
    Bioprocess Biosyst Eng, 2014 Aug;37(8):1679-84.
    PMID: 24554082 DOI: 10.1007/s00449-014-1140-6
    Pleurotus pulmonarius F043, a fungus collected from tropical rain forest, was used to degrade pyrene, a four-rings polycyclic aromatic hydrocarbons (PAHs), in a mineral medium broth. A maximum degradation rate of pyrene (90 %) was occurred at pH 3 and the lowest degradation rate was found in the culture at pH 10 (2 %). More than 90 % pyrene degradation was achieved at pH ranged from 3 to 5, whereas the degradation rate significantly declined when the pH was >5. The degradation of pyrene increased from 2 to 96 % when the temperature rose from 4 to 25 °C. When the temperature was increased to 60 °C resulting the lowest degradation rate into 7 %. Among the agitation rates tested, 120 rpm was the best with 95 % degradation, followed by 100 rpm (90 %). The optimum agitation range for pyrene degradation by P. pulmonarius F043 was 100-120 rpm. Among all the concentrations tested, 0.5 % Tween 80 was the best with 98 % degradation, followed by 1 % Tween 80 (90 %). The optimum concentration of Tween 80 for pyrene degradation by P. pulmonarius F043 was 0.5-1 %. The degradation rate decreased, while the concentration of Tween 80 was increased. The metabolic product was found during degradation process through the identification of gentisic acid by TLC, UV-Spectrophotometer, and GC-MS.
  9. Ahmad Z, Don MM, Mortan SH, Noor RA
    Bioprocess Biosyst Eng, 2010 Jun;33(5):599-606.
    PMID: 19915872 DOI: 10.1007/s00449-009-0381-2
    Recently, the increased demand of fructooligosaccharides (FOS) as a functional food has alarmed researchers to screen and identify new strains capable of producing fructosyltransferase (FTase). FTase is the enzyme that converts the substrate (sucrose) to glucose and fructose. The characterization of complex sugar such as table sugar, brown sugar, molasses, etc. will be carried out and the sugar that contained the highest sucrose concentration will be selected as a substrate. Eight species of macro-fungi will be screened for its ability to produce FTase and only one strain with the highest FTase activity will be selected for further studies. In this work, neural networks (NN) have been chosen to model the process based on their excellent 'resume' in coping with nonlinear process. Bootstrap re-sampling method has been utilized in re-sampling the data in this work. This method has successfully modeled the process as shown in the results.
  10. Saat MN, Annuar MS, Alias Z, Chuan LT, Chisti Y
    Bioprocess Biosyst Eng, 2014 May;37(5):765-75.
    PMID: 24005762 DOI: 10.1007/s00449-013-1046-8
    Production of extracellular laccase by the white-rot fungus Pycnoporus sanguineus was examined in batch submerged cultures in shake flasks, baffled shake flasks and a stirred tank bioreactor. The biomass growth in the various culture systems closely followed a logistic growth model. The production of laccase followed a Luedeking-Piret model. A modified Luedeking-Piret model incorporating logistic growth effectively described the consumption of glucose. Biomass productivity, enzyme productivity and substrate consumption were enhanced in baffled shake flasks relative to the cases for the conventional shake flasks. This was associated with improved oxygen transfer in the presence of the baffles. The best results were obtained in the stirred tank bioreactor. At 28 °C, pH 4.5, an agitation speed of 600 rpm and a dissolved oxygen concentration of ~25 % of air saturation, the laccase productivity in the bioreactor exceeded 19 U L(-1 )days(-1), or 1.5-fold better than the best case for the baffled shake flask. The final concentration of the enzyme was about 325 U L(-1).
  11. Hadibarata T, Zubir MM, Rubiyatno, Chuang TZ
    Bioprocess Biosyst Eng, 2013 Sep;36(9):1229-33.
    PMID: 23135490 DOI: 10.1007/s00449-012-0850-x
    Armillaria sp. F022, a white-rot fungus isolated from decayed wood in tropical rain forest was used to biodegrade anthracene in cultured medium. The percentage of anthracene removal by Armillaria sp. F022 reached 13 % after 7 days and at the end of the experiment, anthracene removal level was at 87 %. The anthracene removal through sorption and transformation was investigated. 69 % of eliminated anthracene was transformed by Armillaria sp. F022 to form other organic structure, while only 18 % was absorbed in the mycelia. In the kinetic experiment, anthracene dissipation will not stop even though the biomass had stopped growing. Anthracene removal by Armillaria sp. F022 was correlated with protein concentration (whole biomass) in the culture. The production of enzyme was affected by biomass production. Anthracene was transformed to two stable metabolic products. The metabolites were extracted in ethyl-acetate, isolated by column chromatography, and then identified using gas chromatography-mass spectrometry (GC-MS).
  12. Hindatu Y, Annuar MSM, Subramaniam R, Gumel AM
    Bioprocess Biosyst Eng, 2017 Jun;40(6):919-928.
    PMID: 28341913 DOI: 10.1007/s00449-017-1756-4
    Insufficient power generation from a microbial fuel cell (MFC) hampers its progress towards utility-scale development. Electrode modification with biopolymeric materials could potentially address this issue. In this study, medium-chain-length poly-3-hydroxyalkanoates (PHA)/carbon nanotubes (C) composite (CPHA) was successfully applied to modify the surface of carbon cloth (CC) anode in MFC. Characterization of the functional groups on the anodic surface and its morphology was carried out. The CC-CPHA composite anode recorded maximum power density of 254 mW/m2, which was 15-53% higher than the MFC operated with CC-C (214 mW/m2) and pristine CC (119 mW/m2) as the anode in a double-chambered MFC operated with Escherichia coli as the biocatalyst. Electrochemical impedance spectroscopy and cyclic voltammetry showed that power enhancement was attributed to better electron transfer capability by the bacteria for the MFC setup with CC-CPHA anode.
  13. Nor NM, Hadibarata T, Zubir MM, Lazim ZM, Adnan LA, Fulazzaky MA
    Bioprocess Biosyst Eng, 2015 Nov;38(11):2167-75.
    PMID: 26275435 DOI: 10.1007/s00449-015-1456-x
    Cresol Red belongs to the triphenylmethane (TPM) class of dyes which are potentially carcinogenic or mutagenic. However, very few studies on biodegradation of Cresol Red were investigated as compared to other type dyes such as azo and anthraquinone dye. The aim of this work is to evaluate triphenylmethane dye Cresol Red degradation by fungal strain isolated from the decayed wood in Johor Bahru, Malaysia. Detailed taxonomic studies identified the organisms as Trichoderma species and designated as strain Trichoderma harzianum M06. In this study, Cresol Red was decolorized up to 88% within 30 days under agitation condition by Trichoderma harzianum M06. Data analysis revealed that a pH value of 3 yielded a highest degradation rate among pH concentrations (73%), salinity concentrations of 100 g/L (73%), and a volume of 0.1 mL of Tween 80 (79%). Induction in the enzyme activities of manganese peroxidase, lignin peroxidase, laccase, 1,2- and 2,3-dioxygenase indicates their involvement in Cresol Red removal. Various analytical studies such as Thin-Layer Chromatography (TLC), UV-Vis spectrophotometer, and Gas chromatography mass spectrometry (GC-MS) confirmed the biotransformation of Cresol Red by the fungus. Two metabolites were identified in the treated medium: 2,4-dihydroxybenzoic acid (t R 7.3 min and m/z 355) and 2-hydroxybenzoic acid (t R 8.6 min and m/z 267). Based on these products, a probable pathway has been proposed for the degradation of Cresol Red by Trichoderma harzianum M06.
  14. Seng B, Kristanti RA, Hadibarata T, Hirayama K, Katayama-Hirayama K, Kaneko H
    Bioprocess Biosyst Eng, 2016 Jan;39(1):81-94.
    PMID: 26522660 DOI: 10.1007/s00449-015-1492-6
    Organic solid waste composting is a complex process that involves many coupled physical, chemical and biological mechanisms. To understand this complexity and to ease in planning, design and management of the composting plant, mathematical model for simulation is usually applied. The aim of this paper is to develop a mathematical model of organic substrate degradation and its performance evaluation in solid waste windrow composting system. The present model is a biomass-dependent model, considering biological growth processes under the limitation of moisture, oxygen and substrate contents, and temperature. The main output of this model is substrate content which was divided into two categories: slowly and rapidly degradable substrates. To validate the model, it was applied to a laboratory scale windrow composting of a mixture of wood chips and dog food. The wastes were filled into a cylindrical reactor of 6 cm diameter and 1 m height. The simulation program was run for 3 weeks with 1 s stepwise. The simulated results were in reasonably good agreement with the experimental results. The MC and temperature of model simulation were found to be matched with those of experiment, but limited for rapidly degradable substrates. Under anaerobic zone, the degradation of rapidly degradable substrate needs to be incorporated into the model to achieve full simulation of a long period static pile composting. This model is a useful tool to estimate the changes of substrate content during composting period, and acts as a basic model for further development of a sophisticated model.
  15. Oon YS, Ong SA, Ho LN, Wong YS, Oon YL, Lehl HK, et al.
    Bioprocess Biosyst Eng, 2016 Jun;39(6):893-900.
    PMID: 26894384 DOI: 10.1007/s00449-016-1568-y
    The main aim of this study is to investigate the performance of organic oxidation and denitrification of the system under long-term operation. The MFC reactor was operated in continuous mode for 180 days. Nitrate was successfully demonstrated as terminal electron acceptor, where nitrate was reduced at the cathode using electron provided by acetate oxidation at the anode. The removal efficiencies of chemical oxygen demand (COD) and nitrate were higher in the closed circuit system than in open circuit system. Both COD and nitrate reduction improved with the increase of organic loading and subsequently contributed to higher power output. The maximum nitrate removal efficiency was 88 ± 4 % (influent of 141 ± 14 mg/L). The internal resistant was 50 Ω, which was found to be low for a double chambered MFC. The maximum power density was 669 mW/m(3) with current density of 3487 mA/m(3).
  16. Liau KF, Shoji T, Ong YH, Chua AS, Yeoh HK, Ho PY
    Bioprocess Biosyst Eng, 2015 Apr;38(4):729-37.
    PMID: 25381606 DOI: 10.1007/s00449-014-1313-3
    A recently reported stable and efficient EBPR system at high temperatures around 30 °C has led to characterization of kinetic and stoichiometric parameters of the Activated Sludge Model no. 2d (ASM2d). Firstly, suitable model parameters were selected by identifiability analysis. Next, the model was calibrated and validated. ASM2d was found to represent the processes well at 28 and 32 °C except in polyhyroxyalkanoate (PHA) accumulation of the latter. The values of the kinetic parameters for PHA storage (q PHA), polyphosphate storage (q PP) and growth (μ PAO) of polyphosphate-accumulating organisms (PAOs) at 28 and 32 °C were found to be much higher than those reported by previous studies. Besides, the value of the stoichiometric parameter for the requirement of polyphosphate for PHA storage (Y PO4) was found to decrease as temperature rose from 28 to 32 °C. Values of two other stoichiometric parameters, i.e. the growth yield of heterotrophic organisms (Y H) and PAOs (Y PAO), were high at both temperatures. These calibrated parameters imply that the extremely active PAOs of the study were able to store PHA, store polyphosphate and even utilize PHA for cell growth. Besides, the parameters do not follow the Arrhenius correlation due to the previously reported unique microbial clade at 28 and 32 °C, which actively performs EBPR at high temperatures.
  17. Oslan SNH, Tan JS, Saad MZ, Halim M, Mohamed MS, Ariff AB
    Bioprocess Biosyst Eng, 2019 Mar;42(3):355-365.
    PMID: 30483888 DOI: 10.1007/s00449-018-2040-y
    Pasteurella multocida serotype B:2 is the causative agent of haemorrhagic septicaemia, a fatal disease in cattle and buffaloes. For use as a vaccine in the treatment of HS disease, an efficient cultivation of attenuated gdhA derivative P. multocida B:2 (mutant) for mass production of viable cells is required. In this study, the role of amino acids and vitamins on the growth of this particular bacterium was investigated. Initially, three basal media (Brain-heart infusion, Terrific broth, and defined medium YDB) were assessed in terms of growth performance of P. multocida B:2. YDB medium was selected and redesigned to take into account the effects of amino acids (glutamic acid, cysteine, glycine, methionine, lysine, tyrosine, and histidine) and vitamins (vitamin B1, nicotinic acid, riboflavin, pyridoxine, pantothenic acid, and biotin). High viable cell number was largely affected by the availability of micronutrient components and macronutrients. Histidine was essential for the growth whereby a traceable amount (20 mM) was found to greatly enhance the growth of gdhA derivative P. multocida B:2 mutant (6.6 × 109 cfu/mL) by about 19 times as compared to control culture (3.5 × 108 cfu/mL). In addition, amongst the vitamins added, riboflavin exhibited the highest impact on the viability of gdhA derivative P. multocida B:2 mutant (5.3 × 109 cfu/mL). Though the combined histidine and riboflavin in the culture eventually did not promote the stacking impact on cell growth and cell viability, nonetheless, they were still essential and important in either growth medium or production medium.
  18. Lian W, Wang W, Tan CP, Wang J, Wang Y
    Bioprocess Biosyst Eng, 2019 Feb;42(2):321-329.
    PMID: 30421172 DOI: 10.1007/s00449-018-2036-7
    LML-type structured lipids are one type of medium- and long-chain triacylglycerols. LML was synthesized using immobilized Talaromyces thermophilus lipase (TTL)-catalyzed interesterification of tricaprylin and ethyl linoleate. The resin AB-8 was chosen, and the lipase/support ratio was determined to be 60 mg/g. Subsequently, the immobilized TTL with strict sn-1,3 regiospecificity was applied to synthesize LML. Under the optimized conditions (60 °C, reaction time 6 h, enzyme loading of 6% of the total weight of substrates, substrate of molar ratio of ethyl linoleate to tricaprylin of 6:1), Triacylglycerols with two long- and one medium-chain FAs (DL-TAG) content as high as 52.86 mol% was obtained. Scale-up reaction further verified the industrial potential of the established process. The final product contained 85.24 mol% DL-TAG of which 97 mol% was LML after purification. The final product obtained with the high LML content would have substantial potential to be used as functional oils.
  19. Hadibarata T, Teh ZC, Rubiyatno, Zubir MM, Khudhair AB, Yusoff AR, et al.
    Bioprocess Biosyst Eng, 2013 Oct;36(10):1455-61.
    PMID: 23334282 DOI: 10.1007/s00449-013-0884-8
    The use of biomaterials or microorganisms in PAHs degradation had presented an eye-catching performance. Pleurotus eryngii is a white rot fungus, which is easily isolated from the decayed woods in the tropical rain forest, used to determine the capability to utilize naphthalene, a two-ring polycyclic aromatic hydrocarbon as source of carbon and energy. In the meantime, biotransformation of naphthalene to intermediates and other by-products during degradation was investigated in this study. Pleurotus eryngii had been incubated in liquid medium formulated with naphthalene for 14 days. The presence of metabolites of naphthalene suggests that Pleurotus eryngii begin the ring cleavage by dioxygenation on C1 and C4 position to give 1,4-naphthaquinone. 1,4-Naphthaquinone was further degraded to benzoic acid, where the proposed terepthalic acid is absent in the cultured extract. Further degradation of benzoic acid by Pleurotus eryngii shows the existence of catechol as a result of the combination of decarboxylation and hydroxylation process. Unfortunately, phthalic acid was not detected in this study. Several enzymes, including manganese peroxidase, lignin peroxidase, laccase, 1,2-dioxygenase and 2,3-dioxygenase are enzymes responsible for naphthalene degradation. Reduction of naphthalene and the presence of metabolites in liquid medium showed the ability of Pleurotus eryngii to utilize naphthalene as carbon source instead of a limited glucose amount.
  20. Luthfi AAI, Tan JP, Harun S, Manaf SFA, Jahim JM
    Bioprocess Biosyst Eng, 2019 Jan;42(1):117-130.
    PMID: 30259181 DOI: 10.1007/s00449-018-2019-8
    Continuous bio-production of succinic acid was reported in homogeneous solid dispersion (HSD) system utilizing porous coconut shell activated carbon (CSAC) as immobilization carrier. The aim of the present work was to implement the HSD system to increase the area of cell immobilization and the rate of succinic-acid production from the lignocellulosic medium. The ratio of the two enzymes (cellulase-to-hemicellulase) was initially optimized to break down the lignocellulose into its free monomers, wherein the best ratio was determined as 4:1. Succinic-acid production was evaluated in the HSD system by varying the substrate loading and dilution rate. The results showed that high productivities of succinic acid were obtained when 60 g/L glucose was fed over a dilution rates ranging from 0.03 to 0.4/h. The titer of succinic acid decreased gradually with higher dilution rate, whereas the residual substrate concentration increased with it. Critical dilution rate was determined to be 0.4/h at which the best productivity of succinic acid of 6.58 g/L h and its yield of 0.66 g/g were achieved using oil palm fronds (OPF) hydrolysate. This work lends evidence to the use of CSAC and lignocellulosic hydrolysate to further exploit the potential economies of scale.
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