Growth and annual production of the brown alga Laminaria religiosa introduced into the Uwa Sea in southern Japan

Recently, aquaculture of Laminaria japonica has expanded to the southern coast of Japan and to China along the East China Sea. The southerly distribution of L. religiosa, compared to that of L. japonica, indicated that the aquaculture of L. religiosa along the southern coasts of Japan might be feasible. Thus, we examined the growth, biomass and productivity of L. religiosa cultivated in the Uwa Sea, in southwestern Japan over a period of two years. The seawater temperature ranged from 12.9 to 27.4°C in 2003/2004 and from 12.2 to 28.3°C in 2004/2005. In 2003/2004, the maximum mean density, maximum mean length, and maximum mean wet weight of L. religiosa was 7.8 ± 5.0 ind. m⁻¹ (mean ± SD), 14.8 ± 4.6 cm, and 1.2 ± 0.8 g wet wt., respectively. In 2004/2005, no germination was confirmed through the study period. The maximum biomass and annual production in 2003/2004 were estimated to be 6.9 ± 5.2 g wet wt. m⁻¹ and 8.9 g wet wt. m⁻¹ year⁻¹, respectively. The present study revealed that L. religiosa cultivated in the Uwa Sea were much smaller compared with those of Hokkaido Island, where the alga is naturally found. For the growth of L. religiosa, a relatively long period of seawater temperatures below 13.5°C is required. In the study area, seawater temperatures were below 13.5°C only 11 days in 2003, and 12 days in 2004. As a result, it is thought that expanding the cultivation of L. religiosa to southern areas including the Uwa Sea will be difficult.     

Growth and annual production of the brown alga Laminaria japonica (Phaeophyta, Laminariales) introduced into the Uwa Sea in southern Japan

The brown alga Laminaria japonica is distributed from southern Hokkaido to the northeastern Honshu in Japan. Recently, aquaculture of L. japonica has expanded to the southern coast of Japan and to China along the East China Sea. In order to elucidate the growth, biomass and productivity of L. japonica in a subtropical area, we cultivated and examined it in the Uwa Sea, in southwestern Japan over a period of 2 years. The seawater temperature ranged from 13.8 to 26.8 °C in 2001/2002 and from 13.1 to 27.2 °C in 2002/2003. In 2001/2002, the maximum density, maximum mean length and maximum mean wet wt. of L. japonica were 59.7 ± 28.0 ind. 50 cm^− 1 (mean ± S.D.), 187.5 ± 82.7 cm (360 cm in the largest individual) and 130.1 ± 94.6 g wet wt., respectively. In 2002/2003, these values were 94.7 ± 22.2 ind. 50 cm^− 1, 159.3 ± 74.4 cm (300 cm in the largest individual) and 95.2 ± 69.5 g wet wt., respectively. Thus, the length and weight increased when the density was low (2001/2002), and the length and weight decreased when the density was high (2002/2003). The maximum biomass was estimated to be 7200 ± 3400 g wet wt. 50 cm^− 1 in 2001/2002 and 7300 ± 2000 g wet wt. 50 cm^− 1 in 2002/2003. Annual production was estimated to be 33.3 kg wet wt. m^− 1 year^− 1 in 2001/2002 and 34.0 kg wet wt. m^− 1 year^− 1 in 2002/2003. The present study indicates that the annual production of L. japonica per rope of 1 m at Uwajima Bay, the Uwa Sea corresponded to 1.1-2.2 m² of that of Hokkaido in their native area. Thus, the present study indicates that L. japonica is highly adaptable because it is able to keep a high level of productivity when grown in water with a high temperature.     

Growth and survival performance of the gametophyte of Gigartina skottsbergii (Rhodophyta, Gigartinales) under defined nutrient conditions in laboratory culture

Gigartina skottsbergii is a commercially important carrageenan producer that has been suffering severe extraction pressure in Chile’s Magellan Region and Cape Horn Archipelago since 1998. In order to create baseline information for its cultivation and repopulation, we studied the effects of agricultural fertilizers on growth of G. skottsbergii early developmental stages. The culture media utilized were: a) seawater + Bayfoland, b) seawater + Superphosphate, c) seawater + Urea, d) seawater + Provasoli and e) seawater as a control. The culture conditions were: a) 12L:12D photoperiod; b) temperature 8 ± 1°C and c) irradiance at 45 μmol photons m⁻² s⁻¹. After 60 days, higher relative growth rates between treatments were observed; the treatments that included Bayfoland and Provasoli showed greater growth (382 ± 55 and 378 ± 50 μm, respectively,) compared to Superphosphate (88 ± 16 μm), control (78 ± 10 μm) and Urea (70 ± 11 μm) treatments, after 81 days. The Urea treatment and the control had inhibitory effects on G. skottsbergii germlings growth and survival, as evidenced by progressive loss of pigmentation and death after 60 days. These results showed that Bayfoland was an excellent alternative to develop cultures.     

Continuous cultures of <Emphasis Type="Italic">Pseudomonas putida</Emphasis> mt-2 overcome catabolic function loss under real case operating conditions

The long-term performance and stability of Pseudomonas putida mt-2 cultures, a toluene-sensitive strain harboring the genes responsible for toluene biodegradation in the archetypal plasmid pWW0, was investigated in a chemostat bioreactor functioning under real case operating conditions. The process was operated at a dilution rate of 0.1 h⁻¹ under toluene loading rates of 259 ± 23 and 801 ± 78 g m⁻³ h⁻¹ (inlet toluene concentrations of 3.5 and 10.9 g m⁻³, respectively). Despite the deleterious effects of toluene and its degradation intermediates, the phenotype of this sensitive P. putida culture rapidly recovered from a 95% Tol⁻ population at day 4 to approx. 100% Tol⁺ cells from day 13 onward, sustaining elimination capacities of 232 ± 10 g m⁻³ h⁻¹ at 3.5 g Tol m⁻³ and 377 ± 13 g m⁻³ h⁻¹ at 10.9 g Tol m⁻³, which were comparable to those achieved by highly tolerant strains such as P. putida DOT T1E and P. putida F1 under identical experimental conditions. Only one type of Tol⁻ variant, harboring a TOL-like plasmid with a 38.5 kb deletion (containing the upper and meta operons for toluene biodegradation), was identified.     

Cultivation of the green alga, Codium fragile (Suringar) Hariot, by artificial seed production in Korea

Codium fragile (Suringar) Hariot is an edible green alga farmed in Korea using seed stock produced from regeneration of isolated utricles and medullary filaments. Experiments were conducted to reveal the optimal conditions for nursery culture and out-growing of C. fragile. Sampling and measurement of underwater irradiance were carried out at farms cultivating C. fragile at Wando, on the southwestern coast of Korea, from October 2004 to August 2005. Growth of erect thalli and underwater irradiance were measured over a range of depths for three culture stages. During the nursery cultivation stage (Stage I), growth rate was greatest at 0.5 m depth (0.055 ± 0.032 mm day⁻¹), where the average midday irradiance over 60 days was 924 ± 32 μmol photons m⁻² s⁻¹. During the pre-main cultivation stage (Stage II), the greatest growth rate occurred at a depth of 2 m (0.113 ± 0.003 mm day⁻¹) with an average irradiance of 248 ± 116 μmol photons m⁻² s⁻¹. For the main cultivation stage (Stage III) of the alga, thalli achieved the greatest increase in biomass at 1 m depth (7.2 ± 1.0 kg fresh wt m⁻¹). These results suggest that optimal growth at each cultivation stages of C. fragile could be controlled by depth of cultivation rope.     

Growth and carrageenan quality of <Emphasis Type="Italic">Kappaphycus striatum</Emphasis> var. <Emphasis Type="Italic">sacol</Emphasis> grown at different stocking densities,duration of culture and depth

Kappaphycus striatum var. sacol was grown in two separate studies: (1) at two stocking densities, and (2) at four different depths, each for three different durations of culture (30, 45 and 60 days) in order to determine the growth rate of the seaweed and evaluate the carrageenan content and its molecular weight. The results demonstrated that stocking density, duration of culture and depth significantly (P < 0.01) affected the growth rate, carrageenan content and molecular weight of K. striatum var. sacol. Decreasing growth rate was observed at both stocking densities and at four depths as duration of culture increased. A lower stocking density (500 g m⁻¹line⁻¹) showed a higher growth rate for the shortest durations, i.e. 30 days, as compared to those grown at a higher density. Likewise, decreasing growth rate was observed as depth increased, except at 50 cm after 60 days of culture. A 45-day culture period produced the highest molecular weight at both stocking densities (500 g m⁻¹line⁻¹ = 1,079.5 ± 31.8 kDa, 1,000 g m⁻¹line⁻¹ = 1,167 ± 270.6 kDa). ‘Sacol’ grown for 30 days at 50 cm (1,178 kDa) to 100 cm (1,200 kDa) depth showed the highest values of molecular weight of carrageenan extracted. The results suggested that K. striatum var. sacol is best grown at a stocking density of 500 g m⁻¹line⁻¹, at a depth of 50–100 cm, and for a duration of 30 days in order to provide the highest growth rate, carrageenan content and molecular weight.     

Hyper production of cellulase-free xylanase by <Emphasis Type="Italic">Thermomyces lanuginosus</Emphasis> SSBP on bagasse pulp and its application in biobleaching

A cellulase-free xylanase production by Thermomyces lanuginosus SSBP using bagasse pulp was examined under submerged (SmC) and solid-state cultivation (SSC). Higher level of xylanase activity (19,320 ± 37 U g⁻¹ dried carbon source) was obtained in SSC cultures than in SmC (1,772 ± 15 U g⁻¹ dried carbon source) after 120 h with 10% inoculum. The biobleaching efficacy of crude xylanase was tested on bagasse pulp, and the maximum brightness of 46.1 ± 0.06% was observed with 50 U of crude xylanase per gram of pulp, which was 3.8 points higher than the brightness of untreated samples. Reducing sugars (26 ± 0.1 mg g⁻¹) and UV-absorbing lignin-derived compounds in the pulp filtrates were observed as maximum in 50 U of crude xylanase-treated samples. T. lanuginosus SSBP has potential applications due to its high productivity of xylanase and its efficiency in pulp bleaching.     

Physiological differences in the growth of <Emphasis Type="Italic">Sargassum horneri</Emphasis> between the germling and adult stages

The effects of temperature, irradiance, and daylength on Sargassum horneri growth were examined at the germling and adult stages to discern their physiological differences. Temperature–irradiance (10, 15, 20, 25, 30°C × 20, 40, 80 μmol photons m⁻²s⁻¹) and daylength (8, 12, 16, 24 h) experiments were carried out. The germlings and blades of S. horneri grew over a wide range of temperatures (10–25°C), irradiances (20–80 μmol photons m⁻²s⁻¹), and daylengths (8–24 h). At the optimal growth conditions, the relative growth rates (RGR) of the germlings were 21% day⁻¹ (25°C, 20 μmol photons m⁻²s⁻¹) and 13% day⁻¹ (8 h daylength). In contrast, the RGRs of the blade weights were 4% day⁻¹ (15°C, 20 μmol photons m⁻²s⁻¹) and 5% day⁻¹ (12 h daylength). Negative growth rates were found at 20 μmol photons m⁻²s⁻¹ of 20°C and 25°C treatments after 12 days. This phenomenon coincides with the necrosis of S. horneri blades in field populations. In conclusion, we found physiological differences between S. horneri germlings and adults with respect to daylength and temperature optima. The growth of S. horneri germlings could be enhanced at 25°C, 20 μmol photons m⁻²s⁻¹, and 8 h daylength for construction of Sargassum beds and restoration of barren areas.     

Optimization of protoplast yields from the red algae <Emphasis Type="Italic">Gracilaria dura</Emphasis> (C. Agardh) J. Agardh and G. <Emphasis Type="Italic">verrucosa</Emphasis> (Huds.) Papenfuss

This study reports on the optimization of protoplast yield from two important tropical agarophytes Gracilaria dura and Gracilaria verrucosa using different cell-wall-degrading enzymes obtained from commercial sources. The conditions for achieving the highest protoplast yield was investigated by optimizing key parameters such as enzyme combinations and their concentrations, duration of enzyme treatment, enzyme pH, mannitol concentration, and temperature. The significance of each key parameter was also further validated using the statistical central composite design. The enzyme composition with 4% cellulase Onozuka R-10, 2% macerozyme R-10, 0.5% pectolyase, and 100 U agarase, 0.4 M mannitol in seawater (30‰) adjusted to pH 7.5 produced the highest protoplast yields of 3.7 ± 0.7 × 10⁶ cells g⁻¹ fresh wt for G. dura and 1.2 ± 0.78 × 10⁶ cells g⁻¹ fresh wt for G. verrucosa when incubated at 25°C for 4–6 h duration. The young growing tips maximally released the protoplasts having a size of 7–15 μm in G. dura and 15–25 μm in G. verrucosa, mostly from epidermal and upper cortical regions. A few large-size protoplasts of 25–35 μm, presumably from cortical region, were also observed in G. verrucosa.     

Artificial Seed Production and Cultivation of the Edible Brown Alga, Sargassum Fulvellum (Turner) C. Agardh: Developing a new Species for Seaweed Cultivation in Korea

Sargassum fulvellum is a brown alga recently introduced to the seaweed cultivation industry in Korea. There is current interest in the commercial scale of aquaculture of this species. For the artificial seeding and cultivation of this alga, growth and maturation were investigated from September 2002 to August 2003. Indoor culture experiments for maturation induction were also conducted at temperatures of 5, 10, 15, 20 and 25 ^∘C and irradiances of 20, 50, 80 and 100 μmol photons m⁻² s⁻¹ under 16:8 h (L:D) photoperiod. Within a given culture test range, higher temperature and irradiance levels favoured the maturation of receptacles in S. fulvellum. Using temperature and irradiance control for thalli, artificial seed production of this species could be done one month earlier than thalli matured in nature. Under natural condition, receptacle formation of the plants began in February, and the eggs were released from March to April. For mature thalli of 200 g wet wt., artificial seeding was complete enough for attachment on seed strings of 100 m. Mean production obtained from the artificial seeding technique in situ was 3.0 kg wet wt m⁻¹ of culture rope during the cultivation period.     

<Emphasis Type="Italic">Iridaea cordata</Emphasis> (Gigartinales,Rhodophyta): responses to artificial UVB radiation

The effects of UVB radiation on the different developmental stages of the carrageenan-producing red alga Iridaea cordata were evaluated considering: (1) carpospore and discoid germling mortality; (2) growth rates and morphology of young tetrasporophytes; and (3) growth rates and pigment content of field-collected plant fragments. Unialgal cultures were submitted to 0.17, 0.5, or 0.83 W m⁻² of UVB radiation for 3 h per day. The general culture conditions were as follows: 12 h light/12 h dark cycles; irradiance of 55 μmol photon^.per square meter per second; temperature of 9 ± 1°C; and seawater enriched with Provasoli solution. All UVB irradiation treatments were harmful to carpospores ( 0.17  \textW \textm ^{- 2} = 40.9 ±6.9% 0.17\;{\text{W}}\,{{\text{m}}^{ - 2}} = 40.9 \pm 6.9\% , 0.5  \textW \textm ^{- 2} = 59.8 ±13.4% 0.5\;{\text{W}}\,{{\text{m}}^{ - 2}} = 59.8 \pm 13.4\% , 0.83  \textW \textm ^{- 2} = 49 ±17.4% 0.83\;{\text{W}}\,{{\text{m}}^{ - 2}} = 49 \pm 17.4\% mortality in 3 days). Even though the mortality of all discoid germlings exposed to UVB radiation was unchanged when compared to the control, those germlings exposed to 0.5 and 0.83 W m⁻² treatments became paler and had smaller diameters than those cultivated under control treatment. Decreases in growth rates were observed in young tetrasporophytes, mainly in 0.5 and 0.83 W m⁻² treatments. Similar effects were only observed in fragments of adult plants cultivated at 0.83 W m⁻². Additionally, UVB radiation caused morphological changes in fragments of adult plants in the first week, while the young individuals only displayed this pattern during the third week. The verified morphological alterations in I. cordata could be interpreted as a defense against UVB by reducing the area exposed to radiation. However, a high level of radiation appears to produce irreparable damage, especially under long-term exposure. Our results suggest that the sensitivity to ultraviolet radiation decreases with increased algal age and that the various developmental stages have different responses when exposed to the same doses of UVB radiation.     

Combined effect of temperature and light intensity on growth and extracellular polymeric substance production by the cyanobacterium Arthrospira platensis

The effects of light intensity and temperature on Arthrospira platensis growth and production of extracellular polymeric substances (EPS) in batch culture were evaluated using a three-level, full-factorial design and response surface methodology. Three levels were tested for each parameter (temperature: 30, 35, 40°C; light intensity: 50, 115, 180 μmol photons m⁻² s⁻¹). Both growth and EPS production are influenced mainly by the temperature factor but the interaction term temperature*light intensity also had a significant effect. In addition, conditions optimising EPS production are different from those optimising growth. The highest growth rate (0.414 ± 0.003 day⁻¹) was found at the lowest temperature (30°C) and highest light intensity (180 μmol photons m⁻² s⁻¹) tested, no optima were detectable within the given test range. Obviously, optima for growth must be at a temperature lower than 30°C and a light intensity higher than 180 μmol photons m⁻² s⁻¹. For EPS production, light intensity had a positive linear effect (optimum obviously higher than 180 μmol photons m⁻² s⁻¹), but for the temperature parameter a maximum effect was detectable at 35°C.     

A preliminary study of the bioremediation potential of Codium fragile applied to seaweed integrated multi-trophic aquaculture (IMTA) during the summer

In integrated multi-trophic aquaculture (IMTA), seaweeds have the capacity to reduce the environmental impact of nitrogen-rich effluents in coastal ecosystems. To establish such bioremediation systems, selection of suitable seaweed species is important. The distribution and productivity of seaweeds vary seasonally based on water temperature and photoperiod. In Korea, candidate genera such as Pophyra, Laminaria, and Undaria grow from autumn to spring. In contrast, Codium grows well at relatively high water temperatures in summer. Thus, aquaculture systems potentially could capitalize on Codium’s capacity for rapid growth in the warm temperatures of late summer and early fall. In this study, we investigated ammonium uptake and removal efficiency by Codium fragile. In laboratory experiments, we grew C. fragile under various water temperatures (10, 15, 20, and 25°C), irradiances (dark, 10, and 100 μmol photons m⁻² s⁻¹), and initial ammonium concentrations (150 and 300 μM); in all cases, C. fragile exhausted the ammonium supply for 6 h. At 150 μM of , ammonium removal efficiency was greatest (99.5 ± 2.6%) when C. fragile was incubated at 20°C under 100 μmol photons m⁻² s⁻¹. At 300 μM of , removal efficiency was greatest (86.3 ± 2.1%) at 25°C under 100 μmol photons m⁻² s⁻¹. Ammonium removal efficiency was significantly greater at 20 and 25°C under irradiance of 100 μmol photons m⁻² s⁻¹ than under other conditions tested.     

Assessment of optimal depth and photon irradiance for cultivation of the brown alga, <Emphasis Type="Italic">Sargassum fulvellum</Emphasis> (Turner) C. Agardh

This study was aimed at determining the optimal depth and photon irradiance for growth of Sargassum fulvellum. Sampling and measurement of underwater irradiance were carried out at farms cultivating S. fulvellum at Wando, southwestern coast of Korea, from May 2004 to April 2005. Growth of thalli, underwater irradiance and photosynthetic quantum yield were measured over a range of depths for three culture stages. During their nursery cultivation stage (Stage I), length increase was greatest at 1.5 m depth (2.5 ± 0.2 cm), where the average midday irradiance over 28 days was 488 ± 58 μmol photons m⁻² s⁻¹. During the pre-main cultivation stage (Stage II), the greatest length increase occurred at 1 m depth (10.9 ± 0.1 cm) with an average irradiance of 845 ± 169 μmol photons m⁻² s⁻¹. For the main cultivation stage (Stage III) of the alga, thalli showed maximal length growth in March and early April at depths of 1–2 m and 3 m. These results suggest that growth at each cultivation stage of S. fulvellum could be controlled by depth of cultivation rope. Presented at the 6th Meeting of the Asian Pacific Society of Applied Phycology, Manila, Philippines.     

A novel cold-adapted lipase from <Emphasis Type="Italic">Acinetobacter</Emphasis> sp. XMZ-26: gene cloning and characterisation

Acinetobacter sp. XMZ-26 (ACCC 05422) was isolated from soil samples obtained from glaciers in Xinjiang Province, China. The partial nucleotide sequence of a lipase gene was obtained by touchdown PCR using degenerate primers designed based on the conserved domains of cold-adapted lipases. Subsequently, a complete gene sequence encoding a 317 amino acid polypeptide was identified. Our novel lipase gene, lipA, was overexpressed in Escherichia coli. The recombinant protein (LipA) was purified by Ni-affinity chromatography, and then deeply characterised. The LipA resulted to hydrolyse pNP esters of fatty acids with acyl chain length from C2 to C16, and the preferred substrate was pNP octanoate showing a k _cat = 560.52 ± 28.32 s⁻¹, K _m = 0.075 ± 0.008 mM, and a k _cat/K _m = 7,377.29 ± 118.88 s⁻¹ mM⁻¹. Maximal LipA activity was observed at a temperature of 15°C and pH 10.0 using pNP decanoate as substrate. That LipA peaked at such a low temperature and remained most activity between 5°C and 35°C indicated that it was a cold-adapted enzyme. Remarkably, this lipase retained much of its activity in the presence of commercial detergents and organic solvents, including Ninol, Triton X-100, methanol, PEG-600, and DMSO. This cold-adapted lipase may find applications in the detergent industry and organic synthesis.     

Zooplankton of two arms in the Morava River floodplain in Slovakia

The species composition, seasonal dynamic of biomass and density of zooplankton were studied in two arms with a different hydrological regime. The samples were collected in two hydrologically different years — extremely wet in 2002 and extremely dry in 2003. In the first arm the mean annual chlorophyll-a concentration was 31.6 μg L⁻¹ (2002) and relatively high 64.7 μg L⁻¹ during 2003. Mean seasonal zooplankton wet biomass was low and varied: 11.6 g m⁻³ (2002) and 2.93 g m⁻³ (2003). Total zooplankton density was high (7,370 N L⁻¹) in 2002, when rotifers predominated in an open water zone and contributed up to 81% of the total zooplankton biomass and 83% of the total zooplankton density. In medial and littoral zone, in total, 22 cladoceran and 15 copepod species were identified. In the second arm the mean annual concentration of chlorophyll-a was high: 74.8 μg L⁻¹ (2002) and 61.4 μg L⁻¹ (2003). Mean seasonal zooplankton wet biomass varied from 92.5 g m⁻³ (2002) and 44.10 g m⁻³ (2003). In 2002 the planktonic crustaceans predominated; their mean biomass was 87.1 g m⁻³ and B. longirostris formed more than 91% of this value. In 2003, the zooplankton density was high (15,687 N L⁻¹), when rotifers contributed up to 94% of this value. The boom of rotifers (58,740 N L⁻¹) was recorded in June 2003. In total, 45 cladoceran and 14 copepod species were recorded in the medial and littoral zones. During observation we concluded that the structure of zooplankton, particularly species composition, abundance, biomass and seasonal dynamics are affected by the fluctuation of water levels in the arms of the rivers’ inundation areas. This unstable hydrological regime prevented the development of planktonic crustaceans.     

The mass cultivation of Ecklonia stolonifera Okamura as a summer feed for the abalone industry in Korea

The mass cultivation of Ecklonia stolonifera Okamura was studied as a possible summer feed for the abalone industry in Korea for the period between August and November when Undaria and Laminaria are not available. Experiments were conducted to investigate the optimal conditions for artificial seed production and mass cultivation of this species. Seedlings of E. stolonifera were reared in an indoor tank for 60 days until they were around 500 μm in length. Following indoor tank culture, the seedlings were transferred in situ to a nursery culture area for 2 months, before begin transferred to the main grow-out area. The maximum growth and development of young thalli in nursery culture area occurred at 2 m depth, whilst maximum growth of thalli in the main culture area occured at 1.5 m depth. Production of E. stolonifera was between 3 and 9 kg wet wt. m⁻¹ in the first year of culture after seeding and 12 to 13 kg wet wt. m⁻¹ in the second year of culture, after management (depth control and fouling organism removal, etc.) of the holdfast. The relationship between optimal water depth for culture and underwater irradiance during the E. stolonifera cultivation was defined as: y = −0.331x + 8.198 (r ² = 0.9903). The growth rates achieved in this trial indicate that E. stolonifera cultures could produce sufficient biomass to supply summer feed for the Korean abalone industry.     

Enhancement of polysaccharides production in <Emphasis Type="Italic">Ganoderma lucidum</Emphasis> by the addition of ethyl acetate extracts from <Emphasis Type="Italic">Eupolyphaga sinensis</Emphasis> and <Emphasis Type="Italic">Catharsius molossus</Emphasis>

To screen stimulators from Chinese medicinal insects for mycelial growth and polysaccharides production of Ganoderma lucidum, G. lucidum was inoculated into the media with and without supplementation of medicinal insect extracts. The ethyl acetate extract of Eupolyphaga sinensis at 55 mg l⁻¹ lead to significant increase in both biomass and intracellular polysaccharides (IPS) concentration from 8.53 ± 0.41 to 14.16 ± 0.43 and 1.28 ± 0.09 to 2.13 ± 0.11 g l⁻¹, respectively. In addition, the ethyl acetate extract of Catharsius molossus at 55 mg l⁻¹ significantly enhanced extracellular polysaccharides (EPS) production; the EPS yield increased from 350.9 ± 14.1 to 475.1 ± 15.3 mg l⁻¹. There were no new components in the two types of polysaccharides obtained by the addition of the insect extracts.     

Phytoplankton biomass and production during late austral spring (1991) and summer (1993) in the Bransfield Strait

Phytoplankton biomass and productivity were measured during two cruises in the Bransfield Strait in December 1991 (D91) and January/February 1993 (J93). Strong seasonal variability in productivity values was observed due to differences in the physiological response of phytoplankton. However, although the photosynthetic capacity of phytoplankton was markedly lower in D91 [P _m ^B =0.61 ± 0.25 mg C (mg Chla)⁻¹ h⁻¹] than in J93 [P _m ^B =2.18 ± 0.91 mg C (mg Chla)⁻¹ h⁻¹], average water column chlorophyll values in different areas of the strait were approximately similar in D91 (49–78 mg Chla m⁻²) and J93 (22–76 mg Chla m⁻²). The spatial distribution of chlorophyll was patchy and generally associated with the influence of the different water masses that meet together in the Bransfield Strait. No correlation was found between the mixed layer depth and either the integrated chlorophyll or the productivity. Our results suggest that major phytoplankton blooms in the Bransfield Strait are advected from the nearby Gerlache Strait or Bellingshausen Sea following the main eastward surface currents. Accepted: 5 July 1998     

Heterologous expression of polyhydroxyalkanoate depolymerase from <Emphasis Type="Italic">Thermobifida</Emphasis> sp. in <Emphasis Type="Italic">Pichia pastoris</Emphasis> and catalytic analysis by surface plasmon resonance

A polyhydroxyalkanote depolymerase gene from Thermobifida sp. isolate BCC23166 was cloned and expressed as a C-terminal His₆-tagged fusion in Pichia pastoris. Primary structure analysis revealed that the enzyme PhaZ-Th is a member of a proposed new subgroup of SCL-PHA depolymerase containing a proline–serine repeat linker. PhaZ-Th was expressed as two glycosylated forms with apparent molecular weights of 61 and 70 kDa, respectively. The enzyme showed esterase activity toward p-nitrophenyl alkanotes with V _max and K _m of 3.63 ± 0.16 μmol min⁻¹ mg⁻¹ and 0.79 ± 0.12 mM, respectively, on p-nitrophenyl butyrate with optimal activity at 50–55°C and pH 7–8. Surface plasmon resonance (SPR) analysis demonstrated that PhaZ-Th catalyzed the degradation of poly-[(R)-3-hydroxybutyrate] (PHB) films, which was accelerated in (R)-3-hydroxyvalerate copolymers with a maximum degradation rate of 882 ng cm⁻² h⁻¹ for poly[(R)-3-hydroxybutyrate-co-3-hydroxyvalerate] (12 mol% V). Surface deterioration, especially on the amorphous regions of PHB films was observed after exposure to PhaZ-Th by atomic force microscopy. The use of P. pastoris as an alternative recombinant system for bioplastic degrading enzymes in secreted form and a sensitive SPR analytical technique will be of utility for further study of bioplastic degradation.