• Proceedings of the Membrane Society of Korea Conference
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• 2003.07a
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• pp.7-10
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• 2003

Factors affecting filtration performance were investigated in a Sequencing Batch Reactor (SBR) coupled with a submerged microfiltration module. Special bioreactors for aerobic and anoxic phases, respectively, were specifically designed in order to differentiate tile effect of Dissolved oxygen (DO) from that of mixing intensity on membrane filterability. DO concentration as well as mixing intensity proved to have a major influence on the membrane performance regardless of the SBR phase. A higher DO concentration resulted in a slower rise in TMP, corresponding to less membrane fouling.

• Horticultural Science & Technology
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• v.33 no.2
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• pp.251-258
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• 2015

Eurycoma longifolia is an important rare medicinal plant that contains valuable bioactive compounds. In the present study, cell suspension culture of E. longifolia was established for the production of biomass and phenolic compounds. Various medium parameters, such as concentration of auxin, salt strength of the medium, and sucrose and nitrogen concentrations, were optimized for the production of biomass at the flask-scale level. Full strength Murashige and Skoog (MS) medium supplemented with $3.0mg{\cdot}L^{-1}$ naphthaleneacetic acid (NAA), 3% (w/v) sucrose, 0:60 $NH{_4}^+:NO{_3}^-$ was found suitable for biomass accumulation. Based on the optimized flask-scale parameters, cell suspension cultures were established in balloon-type bubble bioreactors, and bioprocess parameters such as inoculum density and aeration rate were optimized. Inoculum density of $50g{\cdot}L^{-1}$ and increasing aeration rate from 0.05 to 0.3 vvm, with increases every 7 days, were suitable for the accumulation of both biomass and phenolic compounds. With the optimized conditions, $14.70g{\cdot}L^{-1}$ dry biomass, $10.33mg{\cdot}g^{-1}$ DW of phenolics and $3.89mg{\cdot}g^{-1}$ DW of flavonoids could be achieved. Phenolics isolated from the cell biomass showed optimal free radical scavenging activity.

• Journal of Plant Biotechnology
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• v.31 no.4
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• pp.301-306
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• 2004

Multiple shoots of garlic (Allium sativum L.) were propagated in bioreactors containing MS medium supplemented with 2% sucrose for 3 weeks. Microbulbs were induced on MS medium supplemented with 0.1mg/L NAA and 11% sucrose for 9 weeks. For multiple shoot proliferation, leaves in the shoot must be removed before cultures. When the multiple shoots were cultured without removal of leaves, more than 90% of hyperhydricity and no microbulb formation were observed. Histological observation also indicated irregular size and shape of the cells in hyperhydricity of the shoot. Microbulbs were strarted to form from the shoot after 7 weeks of culture by protuberance of adventitious shoot buds followed by inner periclinal divisions and simultaneous anticlinical division in the epidermis of meristematic bulge. Analysis of ploidy level indicated no phenotypic variations in both multiple shoots and microbulbs induced from the mother plant, suggesting genetic homogeneity among the regenerants.

• BMB Reports
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• v.44 no.2
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• pp.87-95
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• 2011

Enzymatic catalysis has been pursued extensively in a wide range of important chemical processes for their unparalleled selectivity and mild reaction conditions. However, enzymes are usually costly and easy to inactivate in their free forms. Immobilization is the key to optimizing the in-service performance of an enzyme in industrial processes, particularly in the field of non-aqueous phase catalysis. Since the immobilization process for enzymes will inevitably result in some loss of activity, improving the activity retention of the immobilized enzyme is critical. To some extent, the performance of an immobilized enzyme is mainly governed by the supports used for immobilization, thus it is important to fully understand the properties of supporting materials and immobilization processes. In recent years, there has been growing concern in using polymeric materials as supports for their good mechanical and easily adjustable properties. Furthermore, a great many work has been done in order to improve the activity retention and stabilities of immobilized enzymes. Some introduce a spacer arm onto the support surface to improve the enzyme mobility. The support surface is also modified towards biocompatibility to reduce non-biospecific interactions between the enzyme and support. Besides, natural materials can be used directly as supporting materials owning to their inert and biocompatible properties. This review is focused on recent advances in using polymeric materials as hosts for lipase immobilization by two different methods, surface attachment and encapsulation. Polymeric materials of different forms, such as particles, membranes and nanofibers, are discussed in detail. The prospective applications of immobilized enzymes, especially the enzyme-immobilized membrane bioreactors (EMBR) are also discussed.

• Journal of Plant Biotechnology
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• v.31 no.3
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• pp.197-201
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• 2004

Shoot clusters were induced from bulb scales of Lilium longiflorum 'Geogia', and proliferated on medium containing 0.5 mg/L BA and 0.5 mg/L IAA. Thereafter, these shoot clusters were cultured in 5 L air-lift bioreactors to form and grow normal bulblets. Number of bulblets increased on medium with 30 g/L sucrose, but growth of bulblets was effective on medium with 60 g/L sucrose. The number of bulblets from shoot clusters had no differences, though bulblet growth was very effective on medium with between full and double strength of MS salts. The inoculation of 100 g shoot clusters as a cultural material was suitable for formation and growth of bulblets in 5 L bioreactors. Air-lift type was more effective for the formation and growth of bulblets than that in ebb and flood one, and 200∼300 mL$.$min$^{-1}$ injection of air was suitable in growth of bulblets.

• Microbiology and Biotechnology Letters
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• v.35 no.1
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• pp.52-57
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• 2007

A gas-circulating bioreactor was used for enrichment of autotrophic methanogens. Mixture of hydrogen and carbon dioxide (5:1) was used as a sole energy and carbon source. Anaerobic digestive sludge isolated from wastewater treatment system was inoculated into the gas-circulating bioreactor. The enrichment of two chemolithotrophic methanogens, Methanobacterium curvum and Methanobacterium oryzae was accomplished in the gas-circulating bioreactor. The enriched bacteria were cultivated in a bioreactor equipped with hollow-fiber hydrogen-supplying system (hollow-fiber bioreactor), and a hybrid-type bioreactor equipped with hollow-fiber hydrogen-supplying system and electrochemical redox control system. The methane productivity was maximally 30% (V/V) in the hollow-fiber bioreactors and 50% (V/V) in the hybrid-type bioreactor.

• Journal of Microbiology and Biotechnology
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• v.27 no.3
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• pp.552-560
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• 2017

Quorum quenching (QQ) bacteria entrapped in a polymeric composite hydrogel (QQ medium) have been successfully applied in membrane bioreactors (MBRs) for effective biofouling control. However, in order to bring QQ technology closer to practice, the physical strength and lifetime of QQ media should be improved. In this study, enforcement of physical strength, as well as an extension of the lifetime of a previously reported QQ bacteria entrapping hollow cylinder (QQ-HC), was sought by adding a dehydration procedure following the cross-linking of the polymeric hydrogel by inorganic compounds like $Ca^{2+}$ and boric acid. Such prepared medium demonstrated enhanced physical strength possibly through an increased degree of physical cross-linking. As a result, a longer lifetime of QQ-HCs was confirmed, which led to improved biofouling mitigation performance of QQ-HC in an MBR. Furthermore, QQ-HCs stored under dehydrated condition showed higher QQ activity when the storage time lasted more than 90 days owing to enhanced cell viability. In addition, the dormant QQ activity after the dehydration step could be easily restored through reactivation with real wastewater, and the reduced weight of the dehydrated media is expected to make handling and transportation of QQ media highly convenient and economical in practice.

• Journal of Microbiology and Biotechnology
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• v.27 no.3
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• pp.573-583
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• 2017

Biofilm formation on the membrane surface results in the loss of permeability in membrane bioreactors (MBRs) for wastewater treatment. Studies have revealed that cellulose is not only produced by a number of bacterial species but also plays a key role during formation of their biofilm. Hence, in this study, cellulase was introduced to a MBR as a cellulose-induced biofilm control strategy. For practical application of cellulase to MBR, a cellulolytic (i.e., cellulase-producing) bacterium, Undibacterium sp. DM-1, was isolated from a lab-scale MBR for wastewater treatment. Prior to its application to MBR, it was confirmed that the cell-free supernatant of DM-1 was capable of inhibiting biofilm formation and of detaching the mature biofilm of activated sludge and cellulose-producing bacteria. This suggested that cellulase could be an effective anti-biofouling agent for MBRs used in wastewater treatment. Undibacterium sp. DM-1-entrapping beads (i.e., cellulolytic-beads) were applied to a continuous MBR to mitigate membrane biofouling 2.2-fold, compared with an MBR with vacant-beads as a control. Subsequent analysis of the cellulose content in the biofilm formed on the membrane surface revealed that this mitigation was associated with an approximately 30% reduction in cellulose by cellulolytic-beads in MBR.

• Journal of Microbiology and Biotechnology
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• v.30 no.8
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• pp.1227-1234
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• 2020

In this study, yeast cell immobilization was carried out in a packed bed reactor (PBR) to investigate the effects of the volumetric capacity of carriers as well as the different fermentation modes on fuel ethanol production. An optimal volumetric capacity of 10 g/l was found to obtain a high cell concentration. The productivity of immobilized cell fermentation was 16% higher than that of suspended-cell fermentation in batch and it reached a higher value of 4.28 g/l/h in repeated batches. Additionally, using this method, the ethanol yield (95.88%) was found to be higher than that of other tested methods due to low concentrations of residual sugars and free cells. Continuous ethanol production using four bioreactors showed a higher productivity (9.57 g/l/h) and yield (96.96%) with an ethanol concentration of 104.65 g/l obtained from 219.42 g/l of initial total sugar at a dilution rate of 0.092 h^-1. Furthermore, we reversed the substrate-feed flow directions in the in-series bioreactors to keep the cells at their highest activity and to extend the length of continuous fermentation. Our study demonstrates an effective method of ethanol production with a new immobilized approach, and that by switching the flow directions, traditional continuous fermentation can be greatly improved, which could have practical and broad implications in industrial applications.

• Journal of Plant Biotechnology
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• v.3 no.2
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• pp.107-112
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• 2001

The kinetics of Ti-transformed Salvia miltiorrhiza cell cultures was studied in 250-$m\ell$ shake flasks by using B5 medium with addition of 30 gfL of sucrose. In the cell cultures, the maximum cell mass obtained was 11.5 g DW/L on day 15. The highest amount of phenolic compounds - rosmarinic acid (RA) and lithospermic acid B (LAB) reached 871.3 mg/L (day 15) and 121.3 mg/L (day 13), respectively. The total tanshinone production, i.e., intracellular plus extracellular cryptotanshinone, tanshinone 1, and tanshinone IIA, was 5.3 mg/L on day 13. For the cultivations in 2.4-L stirred bioreactors, the residual sugar level and medium conductivity were a little higher in a small turbine impeller reactor ($T_s$) than those in a large turbine impeller reactor ($T_L$), while a higher cell density was obtained in the $T_L$. For the production of tanshinones and phenolics, better results were obtained in the $T_L$ than in the $T_s$. In the $T_L$, similar or even a little higher production titers of tanshinones and phenolic compounds were achieved compared to those in the flasks. The results suggest that the shake flask results could be successfully scaled up to the $T_L$ reactor. Such a large impeller reactor like $T_L$ may be better than a small impeller one for the large-scale production of the valuable metabolites by the suspension cultures of Ti transformed S.miltiorrhiza cells. This is considered due to the beneficial culture environment in the $T_L$, such as low shear rates as estimated theoretically.