Combination effect of lactoalbumin hydrolysate and methyl jasmonate on ginsenoside and polysaccharide production in <Emphasis Type="Italic">Panax quinquefolium</Emphasis> L. cells cultures

Lactoalbumin hydrolysate (LH) at 100 mg L⁻¹ with methyl jasmonate (MJ) at 2 mg L⁻¹ synergistically stimulated ginsenoside accumulation in Panax quinquefolium cells compared with 100 mg L⁻¹ LH. Combination elicitors led to higher ginsenoside productivity (45.93 mg L⁻¹) than single treatment of 100 mg L⁻¹ LH (31.37 mg L⁻¹). This present result will be helpful in providing a tool for enhancing the productivity of ginsenoside by Panax quinquefolium cell cultures on a commercial scale.     

The viability to a wall shear stress and propagation of <Emphasis Type="Italic">Bifidobacterium longum</Emphasis> in the intensive membrane bioreactor

Bifidobacterium longum grew at 65 L pilot scale of the membrane bioreactor (MBR), externally fitted with ceramic membrane (0.7 m²). Cell mass at the MBR reached 22.18 g L⁻¹ as dry cell weight in 12 h, which is 8.44 times higher than cell mass attained at the vial culture. The growth rate in the vial culture was μ = 0.385 h⁻ and at the batch culture was μ = 1.13 h⁻ in the exponential period and μ = 0.31 h⁻¹ in the stationary period. In the fed-batch mode was μ = 1.102 h⁻¹ for 6 h with inoculation and declined to μ = 0.456 h⁻¹ with feeding of feed medium. The growth rate at the MBR was μ = 0.134 h⁻¹. The number of viable cells was 6.01 × 10¹² cfu L⁻¹ at the batch culture, but increased to 1.15 × 10¹⁴ cfu L⁻¹ at the MBR culture. The specific growth rate of viable cell number (colony-forming units per liter, per hour) improved by 6.01 times from the batch to the MBR culture. The wall shear stress mainly generated by the pump, and the membrane incorporated into the MBR was controlled during the cultivation at the MBR. The viability of B. longum declined to under 10% in the first 2 weeks of the 4-week stability test (40°C) as B. longum was exposed to over wall shear stress 713 Pa, but the viability improved to 30–40% in wall shear stress of 260 Pa or STR culture. The loss in the cell viability can be saved by managing with wall shear stress during the cultivation at the MBR.     

Production of saponions and polysaccharide in the presence of lactoalbumin hydrolysate in <Emphasis Type="Italic">Panax quinquefolium</Emphasis> L. cells cultures

In this article, ginsenosides and polysaccharide contents in suspension cells and native roots of Panax quinquefolium L. were studied. In order to enhance the contents of ginsenosides and polysaccharide in P. quinquefolium suspension cells, we tested the effects of lactoalbumin hydrolysate on the growth of P. quinquefolium suspension cell, synthesis of ginsenosides and polysaccharide in flask and bioreactor. In flask culture, cells growth ratio was significantly enhanced by the addition of lower concentration of lactoalbumin hydrolysate. Addition of 100 mg L⁻¹ lactoalbumin hydrolysate significantly enhanced the contents of total saponins (5.44 mg g⁻¹ DW) and the contents were 3.89-fold over the control group. Addition of lactoalbumin hydrolysate significantly promoted the accumulation of polysaccharide, except 200 mg L⁻¹ lactoalbumin hydrolysate. The highest total saponins yield (36.72 mg L⁻¹ DW) and polysaccharide yield (0.83 g L⁻¹ DW) were obtained at 100 mg L⁻¹ lactoalbumin hydrolysate. In a 5-L stirred tank bioreactor, the highest contents of total saponins and TRb group ginsenosides were achieved on day 26, while the effect of lactoalbumin hydrolysate on the contents of TRg group ginsenosides were insignificant. This result suggests that lactoalbumin hydrolysate might have triggered the enzyme activities for the synthesis of TRb group ginsenosides. Overall, the highest total saponins yield (31.37 mg L⁻¹ DW) and polysaccharide yield (1.618 g L⁻¹ DW) were obtained on day 26 and day 24 respectively and the polysaccharide yield was 1.95-fold higher than the shake flask culture (0.83 g L⁻¹ DW). These results provided theoretical reference for two-stage culture in suspension cells of P. quinquefolium in bioreactor.     

Production of high-density Chlorella culture grown in fermenters

The freshwater microalga Chlorella vulgaris was grown heterotrophically in fed-batch 50–600-L fermenters at 36°C, on aerated and mixed nutrient solution with urea as a nitrogen and glucose as a carbon and energy source. Cell density increased from the initial value 6.25 to 117.18 g DW L⁻¹ in 32 h in the fermenter 50 L at a mean growth rate 3.52 g DW L⁻¹ h⁻¹. The DW increase in the fermenter 200 L was from 7.25 to 94.82 g DW L⁻¹ in 26.5 h at a mean growth rate 3.37 g DW L⁻¹ h⁻¹. Mean specific growth rate μ was about 0.1 h⁻¹ in the both fermenters, if nutrients and oxygen were adequately supplied. The DW increase in the fermenter 600 L was from 0.8 to 81.6 g DW L⁻¹ in 66.5 h at a mean growth rate 1.22 g DW L⁻¹ h⁻¹ and μ = 0.07 h⁻¹. A limitation of the cell growth rate in 600 L fermenter caused by a low dissolved oxygen concentration above cell densities higher than 10 g DW L⁻¹) occurred. Specific growth rate decreased approximately linearly with increasing glucose concentration (25–80 g glucose L⁻¹) at the beginning of cultivation and decreased with the time of cultivation. The cell yield was 0.55–0.69 g DW (g glucose)⁻¹. The content of proteins, β-carotene, and chlorophylls in the cells steadily increased and starch content decreased, by keeping aerated and mixed culture another 12 h in fermenter after the cell growth was stopped due to glucose deficiency.     

Effect of nitrite on growth and microcystins production of <Emphasis Type="Italic">Microcystis aeruginosa</Emphasis> PCC7806

As a common pollutant, nitrite concentrations can approach 15 mg NO₂⁻-N L⁻¹ in some aquatic systems. Microcystis aeruginosa blooms are common and widespread in eutrophic freshwater bodies. In this study, M. aeruginosa was exposed to nitrite concentrations ranging from 0 to 15 mg NO₂⁻-N L⁻¹, and the responses of M. aeruginosa were investigated. The specific growth rates, maximum cell densities, light-saturated photosynthetic rates (P_m ^chla ), dark respiration rates (R_d ^chla ), and apparent photosynthetic efficiencies (α^chla ) showed a significant decline with nitrite concentrations increasing. Electrical conductivity and malondialdehyde contents investigation revealed cell membrane damage and apparent leakage of intracellular contents under high nitrite level conditions due to oxidative stress enhancement. Intracellular microcystin (MC)-LR content reached the highest value at 10 mg NO₂⁻-N L⁻¹; however, extracellular MC-LR contents showed a continuous increase until 15 mg NO₂⁻-N L⁻¹ owing to the increasing leakage of intracellular contents. These results elucidated that the high-level nitrite inhibited M. aeruginosa growth by rising oxidative stress, damaging cell membrane, and reducing photosynthesis. However, the moderate increase in nitrite concentrations promoted toxin production and release of toxin.     

Effects of manganese on the growth,photosystem II and SOD activity of the dinoflagellate <Emphasis Type="Italic">Amphidinium</Emphasis> sp.

Experimental ecology methods and chlorophyll fluorescence technology were used to study the effects of different concentrations of manganese (10⁻¹²– 10⁻⁴ mol L⁻¹) on the growth, photosystem II and superoxide dismutase (SOD) activity of Amphidinium sp. MACC/D31. The results showed that manganese had a significant effect on the growth rate, fluorescence parameters (maximal photochemical efficiency of PSII (F _v /F _m ), photochemical quenching (qP) and non-photochemical quenching (NPQ)) in the exponential stage (days 1–3) and SOD activity of Amphidinium sp. (P < 0.05). F _v/F _m in the exponential stage in 10⁻¹² mol L⁻¹ manganese concentration was significantly lower whilst qP and NPQ significantly higher than those in the other concentrations. F _v /F _m (days 6–9) in 10⁻⁴ mol L⁻¹ manganese was significantly higher than those in the other concentrations. F _v /F _m (days 3–6) increased with increased concentration of manganese from 10⁻¹² to 10⁻⁴ mol L⁻¹. The values of qP and NPQ decreased with decreased concentrations of manganese, except for those in days 4–6. F _v /F _m under each concentration increased earlier and decreased later with culture stage whilst NPQ decreased earlier and increased later. The SOD activity increased with increased concentration of manganese from 10⁻¹² to 10⁻⁸ mol L⁻¹. The SOD activity in 10⁻⁴ mol L⁻¹ manganese was significantly higher than those in the other concentrations and in 10⁻¹² mol L⁻¹ manganese, it was significantly lower than those in the other concentrations.     

Evaluation of green fluorescent protein as a reporter gene and phosphinothricin as the selective agent for achieving a higher recovery of transformants in cucumber (<Emphasis Type="Italic">Cucumis sativus</Emphasis> L. cv. Poinsett76) via <Emphasis Type="Italic">Agrobacterium tumefaciens</Emphasis>

Efficient Agrobacterium tumefaciens-mediated transformation and a higher recovery of transformed plants of cucumber cv. Poinsett76 were achieved via direct organogenesis from cotyledon explants. Stable transformants were obtained by inoculating explants with A. tumefaciens strains EHA105 or LBA4404, both harboring the binary vector pME508, which contains the neomycin phosphotransferase II (nptII) and phosphinothricin resistance genes (bar) conferring resistance to kanamycin and PPT, respectively, as selectable markers and the sgfp-tyg gene for the green fluorescent protein (GFP) as a visual marker driven by the constitutive CaMV35S promoter in the presence of acetosyringone (50 μM). Transformed shoots were obtained on MS Murashige and Skoog (Plant Physiol. 15: 473–497, 1962) medium supplemented with 1 mg L⁻¹ benzyladenine (BA), 20 mg L⁻¹ l-glutamine and 2 mg L⁻¹ phosphinothricin (PPT) or 100 mg L⁻¹ kanamycin. The regenerated shoots were examined in vivo using a hand-held long wave UV lamp for GFP expression. The GFP screening helped identify escapes and chimeric shoots at regular intervals to increase the growth of transformed shoots on cotyledon explants. Elongation and rooting of putative transformants were achieved on PPT (2 mg L⁻¹) containing MS media with 0.5 mg L⁻¹ gibberellic acid (GA₃) and 0.6 mg L⁻¹ indole butyric acid (IBA), respectively. PCR and Southern analyses confirmed the integration of the sgfp gene into the genome of T₀ and the progenies. T₁ segregation of transgenic progeny exhibited Mendelian inheritance of the transgene. The use of EHA105 resulted in 21% transformation efficiency compared to 8.5% when LBA4404 was used. This higher rate was greatly facilitated by PPT selection coupled with effective screening of transformants for GFP expression, thus making the protocol highly useful for the recovery of a higher number of transgenic cucumber plants.     

Bioreduction of Cu(II) by Cell-Free Copper Reductase from a Copper Resistant <Emphasis Type="Italic">Pseudomonas</Emphasis> sp. NA

Environmental copper contamination is a serious human health problem. Copper reductase is produced by microorganisms to facilitate copper uptake by ATPases into the cells increasing copper biosorption. This study assessed the reduction of Cu(II) by cell-free extracts of a highly copper-resistant bacterium, Pseudomonas sp. strain NA, isolated from vineyard soil contaminated with copper. Both intact cells and cell-free extract of Pseudomonas sp. strain NA displayed substantial reduction of Cu(II). Intact cells reduced more then 80 mg L⁻¹ of Cu(II) from medium amended with 200 mg L⁻¹ of copper after 24 h of incubation. Cell-free extract of the isolate reduced more than 65% of the Cu(II) at initial copper concentration of 200 mg L⁻¹ after 24 h. Soluble protein production was high at 72 h of incubation at 100 mg L⁻¹ of copper, with more then 60 μg L⁻¹ of total soluble protein in cell-free extract recorded. Cu(II) reduction by isolate NA was increased when copper concentration increased for both intact cells and cell-free extract. Results indicate that Pseudomonas sp. strain NA produces copper reductase enzyme as the key mechanism of copper biotransformation.     

The role of platelet ice microalgae in seeding phytoplankton blooms in Terra Nova Bay (Ross Sea,Antarctica): a mesocosm experiment

The aim of this study was to assess the role of platelet ice microalgal communities in seeding pelagic blooms. Nutrient dynamics, microalgal biomass, photosynthetic parameters, cell densities and species succession were studied in two mesocosm experiments, designed to simulate the transition of microalgal communities from platelet ice habitat to pelagic conditions. The microalgal assemblages were dominated by diatoms, 70% of which were benthic species such as Amphiprora kufferathii, Nitzschia stellata, and Berkeleya adeliensis. Photoacclimation of benthic species was inadequate also at relatively low irradiances. Exceptional growth capacity at different light levels was observed for pelagic species such as Fragilariopsis cylindrus and Chaetoceros spp. which may be important in seeding blooms at ice breakup. Fragilariopsis cylindrus showed high growth rates both at 65 and 10% of incident light and in nutrient replete as well as in nutrient depleted conditions. Five days after inoculation, phytoplankton biomass increased and nutrient concentrations decreased in both light conditions. Nutrient uptake rates were up to 9.10 μmol L⁻¹ d⁻¹ of TIN in the high light tank and 6.18 μmol L⁻¹ d⁻¹ in the low light tank and nutrient depletion in the high light tank occurred 3 days prior to depletion in the low light tank. At nutrient depletion, biomass concentrations were similar in both tanks, 30 and 34 μg Chla L⁻¹. This article belongs to a special topic: Five articles on Sea-ice communities in Terra Nova Bay (Ross Sea), coordinated by L. Guglielmo and V. Saggiomo, appear in this issue of Polar Biology. The studies were conducted in the frame of the National Program of Research in Antarctica (PNRA) of Italy.     

Effects of Artemisinin Derivative on the Growth Metabolism of <Emphasis Type="Italic">Tetrahymena thermophila</Emphasis> BF5 Based on Expression of Thermokinetics

The toxic effects of artesunate and dihydroartemisinin on the growth metabolism of Tetrahymena thermophila BF5 were studied by microcalorimetry. The results showed that: (1) low concentrations of artesunate (≤1 mg L⁻¹) and dihydroartemisinin (≤ 2 mg L⁻¹) promoted the growth metabolism of T. thermophila BF5, whereas high concentrations of artesunate (1–60 mg L⁻¹) and dihydroartemisinin (2–60 mg L⁻¹) inhibited its growth; (2) the half inhibition concentrations IC₅₀ of artesunate and dihydroartemisinin were 17.5817 and 9.5089 mg L⁻¹, respectively. It was concluded that the inhibition of dihydroartemisinin was stronger than that of artesunate.     

A process for the production of ectoine and poly(3-hydroxybutyrate) by <Emphasis Type="Italic">Halomonas boliviensis</Emphasis>

The paper reports a study involving the use of Halomonas boliviensis, a moderate halophile, for co-production of compatible solute ectoine and biopolyester poly(3-hydroxybutyrate) (PHB) in a process comprising two fed-batch cultures. Initial investigations on the growth of the organism in a medium with varying NaCl concentrations showed the highest level of intracellular accumulation of ectoine (0.74 g L⁻¹) at 10–15% (w/v) NaCl, while at 15% (w/v) NaCl, the presence of hydroxyectoine (50 mg L⁻¹) was also noted. On the other hand, the maximum cell dry weight and PHB concentration of 10 and 5.8 g L⁻¹, respectively, were obtained at 5–7.5% (w/v) NaCl. A process comprising two fed-batch cultivations was developed—the first culture aimed at obtaining high cell mass and the second for achieving high yields of ectoine and PHB. In the first fed-batch culture, H. boliviensis was grown in a medium with 4.5% (w/v) NaCl and sufficient levels of monosodium glutamate, NH₄⁺, and PO₄³⁻. In the second fed-batch culture, the NaCl concentration was increased to 7.5% (w/v) to trigger ectoine synthesis, while nitrogen and phosphorus sources were fed only during the first 3 h and then stopped to favor PHB accumulation. The process resulted in PHB yield of 68.5 wt.% of cell dry weight and volumetric productivity of about 1 g L⁻¹ h⁻¹ and ectoine concentration, content, and volumetric productivity of 4.3 g L⁻¹, 7.2 wt.%, and 2.8 g L⁻¹ day⁻¹, respectively. At salt concentration of 12.5% (w/v) during the second cultivation, the ectoine content was increased to 17 wt.% and productivity to 3.4 g L⁻¹ day⁻¹.     

Response of cyanobacteria to arsenic toxicity

Arsenic content of cyanobacterial biomass, soil and water samples from arsenic-contaminated area of eastern India were estimated. It was found that arsenic content in cyanobacterial biomass (276.9 μg g⁻¹) was more than soil (19.01 μg g⁻¹) or water sample (244.13 μg L⁻¹). Shallow tube well water showed more arsenic (244.13 μg L⁻¹) than deep tube well water (146.13 μg L⁻¹). Arsenic resistant genera recorded from the contaminated area were Oscillatoria princeps, Oscillatoria limosa, Anabaena sp. and Phormidium laminosum. Among these, P. laminosum was isolated and exposed to different concentration of Arsenic in vitro (0.1–100 ppm) to study the toxicity level of arsenic. Modulation in stress enzymes and stress-related compounds were studied in relation to lipid peroxidase, catalase, super oxide dismutase (SOD), ascorbate peroxidase (APX), reduced glutathione and carotenoids in arsenic exposed biomass to understand the resistance mechanism of the genus both in laboratory condition as well as in natural condition. Arsenic content of cyanobacterial biomass from contaminated area was more (276.9 μg g⁻¹) than laboratory exposed sample (37.17 μg g⁻¹), indicating bioconcentration of arsenic in long-term-exposed natural biomass. Overall, more activity of catalase was recorded in cyanobacterial biomass of natural condition whereas SOD and APX were at higher level in laboratory culture.     

Long-term cultured callus and the effect factor of high-frequency plantlet regeneration and somatic embryogenesis maintenance in <Emphasis Type="Italic">Zoysia japonica</Emphasis>

In this study, we have demonstrated that Zoysia japonica callus induced from mature seeds can produce high frequencies of plant regeneration and somatic embryogenesis, even following a prolonged period of subculturing. Initial callus cultures were induced from mature seeds of Japanese lawngrass (Z. japonica Steud.) incubated on a medium containing major N₆ medium salts, minor Murashige and Skoog (MS) medium salts, and modified MS medium organic elements supplemented with 3 mg L⁻¹ 2,4-dichlorophenoxyacetic acid (2,4-D) and 0.01–0.02 mg L⁻¹ 6-benzyladenine. Compact callus were selected and subcultured monthly on a medium containing 2 mg L⁻¹ 2,4-D, 0.5 mg L⁻¹ kinetin, 500 mg L⁻¹ casein hydrolysate, 500 mg L⁻¹ proline, and 500 mg L⁻¹ myoinositol. Callus maintained in vitro for 18 mo could be induced to regenerate plantlets with a frequency of >90%. By contrast, 36-mo-old callus cultures failed to produce normal shoot regeneration. However, the addition of CuSO₄ to the subculture media maintained >90% regeneration frequencies in such long-term callus cultures. Histological observations revealed that plant regeneration occurred both through somatic embryogenesis and organogenesis pathways. The ability to sustainable regeneration in long-term callus cultures will be valuable to the program of genetic transformation and somaclonal variant selection.     

Continuous bio-catalytic conversion of sugar mixture to acetone–butanol–ethanol by immobilized <Emphasis Type="Italic">Clostridium acetobutylicum</Emphasis> DSM 792

Continuous production of acetone, n-butanol, and ethanol (ABE) was carried out using immobilized cells of Clostridium acetobutylicum DSM 792 using glucose and sugar mixture as a substrate. Among various lignocellulosic materials screened as a support matrix, coconut fibers and wood pulp fibers were found to be promising in batch experiments. With a motive of promoting wood-based bio-refinery concept, wood pulp was used as a cell holding material. Glucose and sugar mixture (glucose, mannose, galactose, arabinose, and xylose) comparable to lignocellulose hydrolysate was used as a substrate for continuous production of ABE. We report the best solvent productivity among wild-type strains using column reactor. The maximum total solvent concentration of 14.32 g L⁻¹ was obtained at a dilution rate of 0.22 h⁻¹ with glucose as a substrate compared to 12.64 g L⁻¹ at 0.5 h⁻¹ dilution rate with sugar mixture. The maximum solvent productivity (13.66 g L⁻¹ h⁻¹) was obtained at a dilution rate of 1.9 h⁻¹ with glucose as a substrate whereas solvent productivity (12.14 g L⁻¹ h⁻¹) was obtained at a dilution rate of 1.5 h⁻¹ with sugar mixture. The immobilized column reactor with wood pulp can become an efficient technology to be integrated with existing pulp mills to convert them into wood-based bio-refineries.     

Somatic embryogenesis and plant regeneration in oil palm using the thin cell layer technique

An efficient procedure has been developed for inducing somatic embryogenesis and regeneration of plants from tissue cultures of oil palm (Elaeis guineensis Jacq.). Thin transverse sections (thin cell layer explants) of different position in the shoot apex and leaf sheath of oil palm were cultivated in Murashige and Skoog (MS) (Physiol Plant 15:473–497, 1962) medium supplemented with 0–450 μM picloram and 2,4-D with 3.0% sucrose, 500 mg L⁻¹ glutamine, and 0.3 g L⁻¹ activated charcoal and gelled with 2.5 g L⁻¹ Phytagel. Embryogenic calluses were evaluated 12 wk after inoculation. Picloram (450 μM) was effective in inducing embryogenic calluses in 41.5% of the basal explants. Embryogenic calluses were maintained on a maturation medium composed of basal media, plus 0.6 μM NAA and 12.30 μM 2iP, 0.3 g L⁻¹ activated charcoal, and 500 mg L⁻¹ glutamine, with subcultures at 4-wk intervals. Somatic embryos were converted to plants on MS medium with macro- and micronutrients at half-strength, 2% sucrose, and 1.0 g L⁻¹ activated charcoal and gelled with 2.5 g L⁻¹ Phytagel.     

Micropropagation and plant regeneration from embryogenic callus of Miscanthus sinensis

Miscanthus sinensis (Poaceae) is a typical perennial giant grass of East Asia. Due to its high photosynthetic efficiency, low input requirements, and high biomass production, M. sinensis shows outstanding potential as a biofuel feedstock. However, the lack of an efficient tissue culture system may limit its utilization potential. Different explants of M. sinensis were evaluated to develop an efficient tissue culture system. Shoot apices from in vitro-germinated seedling explants were tested for adventitious bud proliferation. The highest level of proliferation (multiplication coefficient 6.69) was obtained when shoot apices were cultured on Murashige and Skoog (MS) medium supplemented with 1.0 mg L⁻¹ 6-benzyladenine (BA), 2.0 mg L⁻¹ kinetin, 0.05 mg L⁻¹ α-naphthalene acetic acid (NAA), 3% sucrose, and 0.8% agar. The highest rooting percentage (95.4%) was obtained when adventitious buds were cultured on half-strength MS medium supplemented with 0.2 mg L⁻¹ NAA, 3% sucrose, and 0.8% agar. Significant differences were found in the formation of embryogenic callus among different explant types. The embryogenic callus derived from epicotyls had the highest regeneration capacity when cultured on a medium supplemented with 2.0 mg L⁻¹ 2,4-dichlorophenoxyacetic acid, 0.5 mg L⁻¹ BA, and 0.1 mg L⁻¹ thiamine. Under these conditions, the callus induction percentage was 82%.     

Anaerobic digestibility of marine microalgae <Emphasis Type="Italic">Phaeodactylum tricornutum</Emphasis> in a lab-scale anaerobic membrane bioreactor

The biomass of industrially grown Phaeodactylum tricornutum was subjected in a novel way to bio-methanation at 33°C, i.e., in an anaerobic membrane bioreactor (AnMBR) at a hydraulic retention time of 2.5 days, at solid retention times of 20 to 10 days and at loading rates in the range of 2.6–5.9 g biomass-COD L⁻¹ day⁻¹ with membrane fluxes ranging from 1 to 0.8 L m⁻² h⁻¹. The total COD recovered as biogas was in the order of 52%. The input suspension was converted to a clear effluent rich in total ammonium nitrogen (546 mg TAN L⁻¹) and phosphate (141 mg PO₄-P L⁻¹) usable as liquid fertilizer. The microbial community richness, dynamics, and organization in the reactor were interpreted using the microbial resource management approach. The AnMBR communities were found to be moderate in species richness and low in dynamics and community organization relative to UASB and conventional CSTR sludges. Quantitative polymerase chain reaction analysis revealed that Methanosaeta sp. was the dominant acetoclastic methanogen species followed by Methanosarcina sp. This work demonstrated that the use of AnMBR for the digestion of algal biomass is possible. The fact that some 50% of the organic matter is not liquefied means that the algal particulates in the digestate constitute a considerable fraction which should be valorized properly, for instance as slow release organic fertilizer. Overall, 1 kg of algae dry matter (DM) could be valorized in the form of biogas (€2.07), N and P in the effluent (€0.02) and N and P in the digestate (€0.04), thus totaling about €2.13 per kilogram algae DM.     

Alginate immobilization of recombinant Escherichia coli whole cells harboring l-arabinose isomerase for l-ribulose production

Recombinant Escherichia coli whole cells harboring Bacillus licheniformis l-arabinose isomerase (BLAI) were immobilized with alginate. The operational conditions for immobilization were optimized with response surface methodology. Optimal alginate concentration, Ca²⁺ concentration, and cell mass loading were 1.8% (w/v), 0.1 M, and 44.5 g L⁻¹, respectively. The interactions between Ca²⁺ concentration, alginate concentration, and initial cell mass were significant. After immobilization of BLAI, cross-linking with 0.1% glutaraldehyde significantly reduced cell leakage. The half-life of immobilized whole cells was 150 days, which was 50-fold longer than that of free cells. In seven repeated batches for l-ribulose production, the productivity was as high as 56.7 g L⁻¹ h⁻¹ at 400 g L⁻¹ substrate concentration. The immobilized cells retained 89% of the initial yield after 33 days of reaction. Immobilization of whole cells harboring BLAI, therefore, makes a suitable biocatalyst for the production of l-ribulose, particularly because of its high stability and low cost.     

Production of hexanoic acid from d-galactitol by a newly isolated Clostridium sp. BS-1

In a study screening anaerobic microbes utilizing d-galactitol as a fermentable carbon source, four bacterial strains were isolated from an enrichment culture producing H₂, ethanol, butanol, acetic acid, butyric acid, and hexanoic acid. Among these isolates, strain BS-1 produced hexanoic acid as a major metabolic product of anaerobic fermentation with d-galactitol. Strain BS-1 belonged to the genus Clostridium based on phylogenetic analysis using 16S rRNA gene sequences, and the most closely related strain was Clostridium sporosphaeroides DSM 1294^T, with 94.4% 16S rRNA gene similarity. In batch cultures, Clostridium sp. BS-1 produced 550 ± 31 mL L⁻¹ of H₂, 0.36 ± 0.01 g L⁻¹ of acetic acid, 0.44 ± 0.01 g L⁻¹ of butyric acid, and 0.98 ± 0.03 g L⁻¹ of hexanoic acid in a 4-day cultivation. The production of hexanoic acid increased to 1.22 and 1.73 g L⁻¹ with the addition of 1.5 g L⁻¹ of sodium acetate and 100 mM 2-(N-morpholino)ethanesulfonic acid (MES), respectively. Especially when 1.5 g L⁻¹ of sodium acetate and 100 mM MES were added simultaneously, the production of hexanoic acid increased up to 2.99 g L⁻¹. Without adding sodium acetate, 2.75 g L⁻¹ of hexanoic acid production from d-galactitol was achieved using a coculture of Clostridium sp. BS-1 and one of the isolates, Clostridium sp. BS-7, in the presence of 100 mM MES. In addition, volatile fatty acid (VFA) production by Clostridium sp. BS-1 from d-galactitol and d-glucose was enhanced when a more reduced culture redox potential (CRP) was applied via addition of Na₂S·9H₂O.     

Production of d-arabitol by a newly isolated Kodamaea ohmeri

A new yeast, isolated from natural osmophilic sources, produces d-arabitol as the main metabolic product from glucose. According to 18S rRNA analysis, the NH-9 strain belongs to the genus Kodamaea. The optimal culture conditions for inducing production of d-arabitol were 37 °C, neutral pH, 220 rpm shaking, and 5% inoculum. The yeast produced 81.2 ± 0.67 g L⁻¹ d-arabitol from 200 g L⁻¹ d-glucose in 72 h with a yield of 0.406 g g⁻¹ glucose and volumetric productivity Q_\textP Q_{\text{P}} of 1.128 g L⁻¹ h⁻¹. Semi-continuous repeated-batch fermentation was performed in shaker-flasks to enhance the process of d-arabitol production by Kodamaea ohmeri NH-9 from d-glucose. Under repeated-batch culture conditions, the highest volumetric productivity was 1.380 g L⁻¹ h⁻¹.