Total Dry Cell Weight Research Articles

Autotrophic poly-3-hydroxybutyrate accumulation in Cupriavidus necator for sustainable bioplastic production triggered by nutrient starvation

Cupriavidus necator is a facultative chemolithoautotrophic bacterium able to convert carbon dioxide into poly-3-hydroxybutyrate. This is highly promising as the conversion process allows the production of sustainable and biodegradable plastics. Poly-3-hydroxybutyrate accumulation is known to be induced by nutrient starvation, but information regarding the optimal stress conditions controlling the process is still heterogeneous and fragmentary. This study presents a comprehensive comparison of the effects of nutrient stress conditions, namely nitrogen, hydrogen, phosphorus, oxygen, and magnesium deprivation, on poly-3-hydroxybutyrate accumulation in C. necator DSM545. Nitrogen starvation exhibited the highest poly-3-hydroxybutyrate accumulation, achieving 54% of total cell dry weight after four days of nutrient stress, and a carbon conversion efficiency of 85%. The gas consumption patterns indicated flexible physiological mechanisms underlying polymer accumulation and depolymerization. These findings provide insights into strategies for efficient carbon conversion into bioplastics, and highlight the key role of C. necator for future industrial-scale applications.

Food waste upcycling via microalgal adaptive evolution for lipids and fatty acids enhancement towards circular bioeconomy

Disposal of food waste (FW) has become a significant problem that exacerbates the economy, environment and climate due to its rich nutrient content, thereby implying the necessity to upcycle FW by biotechnology means in a sustainable manner. Employing photosynthetic microalgae to FW upcycling hold great potential to simultaneously remediate the FW and to biosynthesize novel commodity metabolites. However, effective nutrient utilization of FW and metabolite overproduction by native algae is inadequate, and thus further development of strain and strategy is warranted to achieve a circular bioeconomy. Here, the marine Nannochloropsis oceanica was improved by adaptive laboratory evolution (ALE) under low salt conditions for enhanced lipid and uncompromised growth features. Then, FW hydrolysate (FWH) was used as the carbon source to facilitate the mixotrophic cultivation of N. oceanica. Results showed that the biomass of scrutinized evolved cells (ALE70) resulted in enhanced biomass production of 830 mg/l using FWH. Interestingly, ALE70 strains accumulate lipids up to 49 % of total cell dry weight, which was 1.5-fold higher than the WT cells cultivated in FWH. Importantly, FAME analysis by GC–MS showed that FWH provision to the ALE70 strains resulted in notable fatty acid alteration, enriched explicitly with unsaturated fatty acid and EPA content was hiked by 32 % of FAME. Altogether, these findings demonstrated a potential duplex strategy by employing the evolved strains to upcycle the food waste for valuable metabolite biosynthesis effectively and also offer promising insights into algal-associated food waste valorization towards circular bioeconomy.

Engineering Nannochloropsis oceanica for the production of diterpenoid compounds.

Photosynthetic microalgae like Nannochloropsis hold enormous potential as sustainable, light-driven biofactories for the production of high-value natural products such as terpenoids. Nannochloropsis oceanica is distinguished as a particularly robust host with extensive genomic and transgenic resources available. Its capacity to grow in wastewater, brackish, and sea waters, coupled with advances in microalgal metabolic engineering, genome editing, and synthetic biology, provides an excellent opportunity. In the present work, we demonstrate how N. oceanica can be engineered to produce the diterpene casbene-an important intermediate in the biosynthesis of pharmacologically relevant macrocyclic diterpenoids. Casbene accumulated after stably expressing and targeting the casbene synthase from Daphne genkwa (DgTPS1) to the algal chloroplast. The engineered strains yielded production titers of up to 0.12 mg g-1 total dry cell weight (DCW) casbene. Heterologous overexpression and chloroplast targeting of two upstream rate-limiting enzymes in the 2-C-methyl- d-erythritol 4-phosphatepathway, Coleus forskohlii 1-deoxy- d-xylulose-5-phosphate synthaseand geranylgeranyl diphosphate synthase genes,further enhanced the yield of casbeneto a titer up to 1.80 mg g-1 DCW. The results presented here form a basis for further development and production of complex plant diterpenoids in microalgae.

Efficient use of discarded vegetal residues as cost-effective feedstocks for microbial oil production

BackgroundHorticultural intensive type systems dedicated in producing greenhouse vegetables are one of the primary industries generating organic waste. Towards the implementation of a zero-waste strategy, this work aims to use discarded vegetables (tomato, pepper and watermelon) as feedstock for producing microbial oil using the oleaginous yeast Cryptococcus curvatus.ResultsThe soluble fraction, resulting after crushing and centrifuging these residues, showed C/N ratios of about 15, with a total carbohydrate content (mainly glucose, fructose and sucrose) ranging from 30 g/L to 65 g/L. Using these liquid fractions as substrate under a pulse-feeding strategy with a concentrated glucose solution resulted in an intracellular total lipid accumulation of about 30% (w/w) of the total dry cell weight (DCW). To increase this intracellular lipid content, the initial C/N content was increased from 15 to 30 and 50. Under these conditions, the process performance of the pulse-feeding strategy increased by 20–36%, resulting in a total intracellular lipid concentration of 35–40% DCW (w/w).ConclusionThese results demonstrate the potential of discarded vegetables as a substrate for producing bio-based products such as microbial oil when proper cultivation strategies are available.

β-glucosidase production by recombinant Pichia pastoris strain Y1433 under optimal feed profiles of fed-batch cultivation.

Pichia pastoris, a methylotrophic yeast, is known to be an efficient host for heterologous proteins production. In this study, a recombinant P. pastoris Y11430 was found better for β-glucosidase activity in comparison with a wild type P. pastoris Y11430 strain, and thereby, subjected to methanol intermittent feed profiling for β-glucosidase production. The results showed that at 72h of cultivation time, the cultures with 16.67% and 33.33% methanol feeding with constant rate could produce the total dry cell weight of 52.23 and 118.55g/L, respectively, while the total mutant β-glucosidase activities were 1001.59 and 3259.82 units, respectively. The methanol feeding profile was kept at 33% with three methanol feeding strategies such as constant feed rate, linear feed rate, and exponential feed rate which were used in fed-batch fermentation. At 60h of cultivation, the highest total mutant β-glucosidase activity was 2971.85 units for exponential feed rate culture. On the other hand, total mutant β-glucosidase activity of the constant feed rate culture and linear feed rate culture were 1682.25 and 1975.43 units, respectively. The kinetic parameters of exponential feed rate culture were specific growth rate on glycerol 0.228/h, specific growth of methanol 0.061/h, maximum total dry cell weight 196.73g, yield coefficient biomass per methanol ([Formula: see text]) 0.57 gcell/gMeOH, methanol consumption rate ([Formula: see text]) 5.76 gMeOH/h, and enzyme productivity ([Formula: see text]) 75.96 units/h. In conclusion, higher cell mass and β- glucosidase activity were produced under exponential feed rate than constant and linear feed rates.

Optimization of Production of Polyhydroxyalkanoates (PHAs) from Newly Isolated Ensifer sp. Strain HD34 by Response Surface Methodology

Petroleum-based plastics have become a big problem in many countries because of their non-degradability and that they become microplastics in the environment. This study focused on the optimization of production medium and conditions of polyhydroxyalkanoates (PHAs), which are biodegradable bioplastics and are accumulated in microbial cells. Among 341 isolates from 40 composted soil samples, the best isolate was the HD34 strain, which was identified using morphological, molecular, and biochemical methods. The results showed that the strain was most closely related to Ensifer adhaerens LMG20216T, with 99.6% similarity. For optimization of production medium and conditions using response surface methodology, it exhibited an optimal medium containing 3.99% (w/v) of potato dextrose broth (PDB) and 1.54% (w/v) of D-glucose with an adjusted initial pH of 9.0. The optimum production was achieved under culture conditions of a temperature of 28 °C, inoculum size of 2.5% (v/v), and a shaking speed of 130 rpm for 5 days. The results showed the highest PHA content, total cell dry weight, and PHA yield as 72.96% (w/w) of cell dry weight, 9.30 g/L, and 6.78 g/L, respectively. The extracted PHA characterization was studied using gas chromatography, 1H NMR, FTIR, and XRD. The results found that the polymer was a polyhydroxybutyrate (PHB) with a melting temperature (Tm) and degradation temperature (Td) of 173.5 °C and 260.8 °C, respectively.

Optimization of silybin production fromSilybum marianumtissue cell cultures using different elicitor solutions

Plant cell cultures of Silybum marianum L. are studied under different classes of elicitors including heavy metal ions (Ag+), polysaccharides (yeast extract and chitosan), and plant response signaling compounds (salicylic acid) in order to enhance silybin production. Remarkably, all elicitors enhanced the accumulation of silybin compared to the control experiment, but the highest total silybin content was achieved in cell suspensions elicited with yeast extract at 0.5 μg.ml−1 producing a total silybin yield at 0.15 mg.g−1 cells dry weight after 2 days of elicitation for a total cell dry weight of 1.49 g. The lowest silybin accumulation belongs to chitosan treatment producing maximum silybin content and dry weight of 0.038 mg.g−1 DW and 1.19 g, respectively. These results are promising to establish a proof of concept using yeast extract as a viable elicitor option to produce silybin in tissue culture. Practical applications Optimization of elicitor-induced cell culture production of secondary metabolites is important to develop a proof concept that can be easily scaled-up and stand as an economically viable solution to meet the increasing demand for health and food supplements. In fact, the production of secondary metabolites from tissue cultures permits space and resource optimization, protects endangered endemic plants, and contributes to food/health security and sustainable development.

Optimization of culture conditions of screened Galactomyces candidum for the production of single cell protein from biogas slurry

The use of single cell protein (SCP) has become a method for alleviating the shortage of protein feed that microorganisms propagate in a suitable culture medium. In this study, SCP was produced by yeast to use the nutrition contained in the biogas slurry of chicken manure. The results showed that Galactomyces candidum was the most efficient at producing SCP among the seven yeasts studied. The maximum cell dry weight (CDW) 6.79 g/L and protein content 39.39%, were obtained under the fermentation conditions of initial NH 4 + -N concentration of 2000 mg/L and a C/N ratio of 6:1 with acetate as the pH regulator. The total CDW increased to 9.24 g/L after secondary fermentation. Metal elements had a little effect on the growth of G. candidum . The addition of sulfur not only promoted the synthesis of sulfur-containing amino acid cysteine but also increased protein content by promoting the synthesis of glutamic acid and glutamine. Future experiments should focus more on achieving high-density cultivation and more efficient utilization of ammonia nitrogen in the biogas slurry. How to cite: Zhou P, Zhang L, Ding H, et al. Optimization of culture conditions of screened Galactomyces candidum for the production of single cell protein from biogas slurry. Electron J Biotechnol 2022;55. https://doi.org/10.1016/j.ejbt.2021.11.006

The production of single cell protein from biogas slurry with high ammonia-nitrogen content by screened Nectaromyces rattus

In this study, a novel method was proposed to obtain single cell protein (SCP) in yeast by using biogas slurry as culture medium. The results show that Nectaromyces rattus was the most efficient at producing SCP among the 7 different yeasts studied. Acetic acid was a better pH regulator than hydrochloric acid. After culture with the initial NH4+-N concentration 2,000 mg/L, C/N ratio 6:1, the initial pH 5.50 and rotation speed of 200 rpm, a total cell dry weight of 12.58 g/L with 35.96% protein content was obtained. Nineteen amino acids accounted for 46.85% of cell dry weight, and proline content was as high as 12.0% of the cell dry weight. However, sulfur-containing amino acids, including methionine and cystine, were deficient. Further research should focus on the high cell density culture to increase SCP production.

<p>Agro-industrial byproducts as alternate cost-effective medium components for production of poly-β-hydroxybutyrate<em></em></p>

Polyhydroxybutyrates (PHBs), biodegradable plastics, having properties similar to conventional plastics, exhibit a high potential for replacing petrochemical-based non-degradable plastics. But a major obstacle in their large-scale commercial production is high production cost, one of the key factors responsible for which is the expensive carbon sources that are currently being used in their manufacturing process. The present work was aimed to study PHB production using cost-effective substrates as carbon sources in the production medium. Inexpensive agro-industrial byproducts (molasses, cheese whey, wheat bran and banana peel, used in different concentrations) were explored for their potential to substitute the conventional costly substrates. Compared to glucose, all the four alternate carbon sources showed an enhancement in PHB production. The mean percent increase in PHB production was in the range of 3.81% to 7.23%. However, some of the bacterial isolates showed an enhancement as high as 23.32% and 19.65%. Highest mean PHB yield was observed in molasses (135.18 mg/mL), followed by cheese-whey (133.79 mg/mL), banana peel, and least in wheat bran based production medium. On dry weight basis, PHB accumulation in cells was observed to be 64.32% and 64.29% of the total dry cell weight with molasses and cheese whey, respectively, as carbon sources. FTIR spectra of extracted PHB were found to be comparable to the spectra of standard PHB, thus, confirming the chemical nature of the extracted polymer.

Lipid Production by Yeasts Growing on Commercial Xylose in Submerged Cultures with Process Water Being Partially Replaced by Olive Mill Wastewaters

Six yeast strains belonging to Rhodosporidium toruloides, Lipomyces starkeyi, Rhodotorula glutinis and Cryptococcus curvatus were shake-flask cultured on xylose (initial sugar—S0 = 70 ± 10 g/L) under nitrogen-limited conditions. C. curvatus ATCC 20509 and L. starkeyi DSM 70296 were further cultured in media where process waters were partially replaced by the phenol-containing olive mill wastewaters (OMWs). In flasks with S0 ≈ 100 g/L and OMWs added yielding to initial phenolic compounds concentration (PCC0) between 0.0 g/L (blank experiment) and 2.0 g/L, C. curvatus presented maximum total dry cell weight—TDCWmax ≈ 27 g/L, in all cases. The more the PCC0 increased, the fewer lipids were produced. In OMW-enriched media with PCC0 ≈ 1.2 g/L, TDCW = 20.9 g/L containing ≈ 40% w/w of lipids was recorded. In L. starkeyi cultures, when PCC0 ≈ 2.0 g/L, TDCW ≈ 25 g/L was synthesized, whereas lipids in TDCW = 24–28% w/w, similar to the experiments without OMWs, were recorded. Non-negligible dephenolization and species-dependent decolorization of the wastewater occurred. A batch-bioreactor trial by C. curvatus only with xylose (S0 ≈ 110 g/L) was performed and TDCW = 35.1 g/L (lipids in TDCW = 44.3% w/w) was produced. Yeast total lipids were composed of oleic and palmitic and to lesser extent linoleic and stearic acids. C. curvatus lipids were mainly composed of nonpolar fractions (i.e., triacylglycerols).

Maximizing Biomass and Lipid Production in Heterotrophic Culture of Chlorella vulgaris: Techno-Economic Assessment

Nowadays, chlorophycean microalgae have attained a broad-spectrum attention as a potential candidate for biomass and bioenergy production. Despite their appreciated benefits, one of major problems is their low biomass and lipid productivity. Here we investigated the heterotrophic culture in shake flasks and stirred tank bioreactor to improve the lipid and biomass production in a naturally isolated strain of Chlorella vulgaris. A naturally isolated C. vulgaris strain was cultivated in BG-11 medium in shake flask and bioreactor. Its biochemical composition and growth kinetic parameters were investigated. The biomass productivity was improved (3.68 fold) under heterotrophic culture compared to basal autotrophic culture condition in shake flask experiment. The total lipid content increased to 44% of total Dry Cell Weight (DCW) during heterotrophic growth after 21 days. Moreover, a great Fatty Acid Methyl Esters (FAME) yield was observed under heterotrophic cultivation. Total biomass and lipid content of microalgae in bioreactor experiment increased to 4.95 and 2.18 g L-1 respectively, during 5 days of the experiment compared to its basic autotrophic culture. The techno-economic aspects of exploiting C. vulgaris as a biodiesel feedstock werealso evaluated. The results imply that heterotrophic cultivation could compensate the low biomass productivity in microalgae for green energy production. Ever growing rates of established patents on application of various genetic and bioengineering-based methods have made it possible to achieve higher lipid contents with reduced total costs for microalgal biodiesel production as well.

Lipid production by Cryptococcus albidus using biowastes hydrolysed by indigenous microbes.

The efficiency of Cryptococcusalbidus was evaluated for its abilities to assimilate onion and apple hydrolysates as a medium for lipid production. Onion waste (OW) and apple waste (AW) were hydrolysed at an organic load of 2% total solids by indigenous microbes under mesophilic conditions. The indigenous microbes effectively hydrolysed both wastes giving the highest reducing sugar content of 4.8g/L and 10.8g/L with OW and AW hydrolysates, respectively. The microbiome analysis revealed that most of the indigenous microbes belonged to genus Bacillus and a significant population of α-proteobacteria and γ-proteobacteria were also present. Cell retention culture of C. albidus at a dilution rate of 0.01h-1 resulted in a total dry cell weight (DCW) of 13.5g/L with an intracellular lipid content of 20.0% at 168h, corresponding to an enhancement of 3.48-folds and 2.37-folds in DCW and lipid concentration, respectively, as compared to batch fermentation.

Translocation and de novo synthesis of eicosapentaenoic acid (EPA) during nitrogen starvation in Nannochloropsis gaditana

The microalga Nannochloropsis gaditana is known for accumulating fatty acids, including the commercially interesting eicosapentaenoic acid (EPA) within the polar lipids (PL) and neutral lipids (NL). During microalgal growth EPA is mainly present in the PL. Upon nitrogen starvation N. gaditana accumulates large amounts of TAG in lipid bodies. The neutral lipid fraction will mainly consist of triacylglycerol (TAG). When expressed per total cell dry weight, the NL-localized EPA increased while the PL-localized EPA decreased, suggesting that EPA is translocated from the PL into the NL lipids during nitrogen starvation. Here, we elucidated the origin of EPA in NL of N. gaditana by firstly growing this microalga under optimal growth conditions with 13CO2 as the sole carbon source followed by nitrogen starvation with 12CO2 as the sole carbon source. By measuring both 12C and 13C fatty acid isotope species in time, the de novo synthesized fatty acids and the already present fatty acids can be distinguished. For the first time, we proved that actual translocation of EPA from the PL into the NL occurs during nitrogen starvation of N. gaditana. Next to being translocated, EPA was synthesized de novo in both PL and NL during nitrogen starvation. EPA was made by carbon reshuffling within the cell as well. EPA was the main fatty acid translocated, suggesting that the enzyme responsible for fatty acid translocation has a high specificity for EPA.

Polyhydroxybutyrate production by an extremely halotolerant Halomonas elongata strain isolated from the hypersaline meromictic Fără Fund Lake (Transylvanian Basin, Romania).

This study aimed at unprecedented physical and chemical evaluation of the 'green plastics' polyhydroxyalkanoates (PHAs), in an extremely halotolerant Halomonas elongata strain 2FF under high-salt concentration. The investigated bacterial strain was isolated from the surface water of the hypersaline Fără Fund Lake. The 16S rRNA gene sequence phylogeny and phenotypic analysis indicated that the isolate belonged to H. elongata. PHA inclusions were observed by Sudan Black B, Nile Red staining, and transmission electron microscopy during growth at high salinity (10%, w/v, NaCl) on 1% (w/v) d-glucose. The produced polymer was quantitatively and qualitatively assessed using crotonic acid assay, elemental analysis, Fourier transform infrared and Raman spectroscopies. Additionally, X-ray powder diffraction, 1 H-NMR spectroscopy, and differential scanning calorimetry were applied. The investigations showed that the intracellular polymer was polyhydroxybutyrate (PHB) of which the strain produced up to 40 wt% of total cell dry weight after 48h. The analysis of phaC gene from the isolated H. elongata strain indicated that the encoded PHA synthase belongs to Class I PHA synthase family. Overall, our investigations pointed out that the halotolerant H.elongata strain 2FF was capable to produce significant amounts of PHB fromd-glucose, and PHAs from various carbon substrates at high-salt concentrations. The tested strain showed the ability for significant production of natural, biodegradable polymers under nutrient limitation and hypersaline conditions suggesting its potentiality for further metabolic and molecular investigations towards enhanced biopolymer production. Additionally, this study reports on the unprecedented use of Raman and XPRD techniques to investigate PHAs of an extremely halotolerant bacterium, thus expanding the repertoire of physical methods to study green plastics derived from extremophilic microorganisms.

Co-production of polyhydroxyalkanoates and carotenoids through bioconversion of glycerol by Paracoccus sp. strain LL1

Polyhydroxyalkanoates (PHA) have emerged as a potential alternative to synthetic plastics, although its large-scale production is limited by the expenditure incurred in feed materials. Co-production of various valuable bioproducts along with PHA has been proposed to alleviate the overall production cost. Here, high-yield co-production of PHA and carotenoids was achieved in single step fermentation by Paracoccus sp. LL1. The halophilic bacterial strain could metabolize a wide range of substrates including methanol, lactose, galactose, glycerol, fructose, mannitol, etc. Under batch fermentation using mineral media supplemented with 2% glycerol, Paracoccus sp. LL1 synthesized 3.77gL−1 PHA with concomitant production of 3.6mgL−1 of carotenoids after 96h. An enhancement of 2.2-folds in total dry cell weight (DCW) was achieved through cell retention culture of Paracoccus sp. LL1, resulting in a maximum DCW (24.2gL−1) containing PHA (39.3%, ww−1) with concomitant enhancement in the production of total carotenoids. Paracoccus sp. LL1 could convert glycerol into carotenoids and PHA to a level of 7.14mgL−1 and 9.52gL−1, respectively. It is the first report showing value addition in PHA production process through co-production of high value carotenoids by Paracoccus sp. using glycerol as substrate.

Development of polyhydroxybutyrate biosynthesis in Bacillus subtilis with combination of PHB-associated genes derived from Ralstonia eutropha and Bacillus megaterium

Abstract Polyhydroxybutyrate (PHB) is a biodegradable polymer synthesized by bacteria for carbon storage in response to environmental stress. B. subtilis is generally recognized as a safe Gram-positive bacterium and is widely used for industrial-scale production of proteins and chemicals. Owing to lack of toxic lipopolysaccharides, B. subtilis is a superior alternative to the Gram-negative bacteria presently used for PHB production. In this study, we introduced PHB synthesis genes from R. eutropha and B. megaterium into B. subtilis for PHB production. The highest yield of PHB was achieved by coexpression of phaA from R. eutropha and phaR, phaB , and phaC from B. megaterium (up to 13.02% ± 1.67% of total cell dry weight in LB medium containing 1% glucose). The results indicate that B. subtilis is potentially used as a safe vehicle for producing PHB.

Efficient conversion of crude glycerol from various industrial wastes into single cell oil by yeast Yarrowia lipolytica

In this study, crude glycerol from various industries was used to produce lipids via wild type Yarrowia lipolytica A101. We tested samples without any prior purification from five different waste products; each contained various concentrations of glycerol (42–87%) as the sole carbon source. The best results for lipid production were obtained for medium containing glycerol from fat saponification. This reached 1.69gL−1 (25% of total cell dry weight) with a biomass yield of 0.17gg−1 in the flasks experiment. The batch cultivation in a bioreactor resulted in enhanced lipid production—it achieved 4.72gL−1 with a biomass yield 0.21gg−1. Moreover, the properly selected batch of crude glycerol provides a defined fatty acid composition. In summary, this paper shows that crude glycerol from soap production could be efficiently converted to single cell oil without any prior purification.

Metabolic engineering of Synechococcus sp. PCC 7002 to produce poly-3-hydroxybutyrate and poly-3-hydroxybutyrate-co-4-hydroxybutyrate

Cyanobacteria are an important group of photoautotrophic bacteria that have been engineered and used to produce a wide range of biomaterials and biofuels, which are usually derived from important intermediates of the central metabolic pathways. In this study, the production of poly-3-hydroxybutyrate and poly-3-hydroxybutyrate-co-4-hydroxybutyrate in cyanobacteria was studied, and metabolic engineering strategies to improve the yields were also investigated. The genes involved in the biosynthetic pathway for poly-3-hydroxybutyrate from Chlorogloeopsis fritschii PCC 9212 were introduced into Synechococcus sp. PCC 7002, and the resulting strain was able to accumulate 2.77% of total cell dry weight as poly-3-hydroxybutyrate. When the ccmR gene was deleted in this strain, the yield of poly-3-hydroxybutyrate increased to 3.97% of total cell dry weight. A biosynthetic pathway for the production of 4-hydroxybutyryl-CoA was also constructed and introduced into the poly-3-hydroxybutyrate-producing strain. The resulting strain was able to produce ~4.5% of total cell dry weight as poly-3-hydroxybutyrate-co-4-hydroxybutyrate, in which 4-hydroxybutyrate accounted for ~12% of the co-polymer. These results demonstrate that poly-3-hydroxybutyrate-co-4-hydroxybutyrate can be produced in cyanobacteria and confirm that succinic semialdehyde is an important TCA cycle metabolite in cyanobacteria. This study also demonstrates the potential for future metabolic engineering in cyanobacteria that is based on recently discovered metabolites.

Potential of Bacillus megaterium for production of polyhydroxyalkanoates using the red algae Gelidium amansii

To investigate the ability to accumulate polyhydroxyalkanoates (PHA) using either acid-treated or un-treated red algae (Gelidium amansii) as a carbon source, a total of six Bacillus megaterium strains were tested. All strains were able to grow considerably when acid-treated algae were used, where strain KCTC 3712 reached highest total dry cell weight (DCW) of 4.1 g/L with a PHA content of 30%. Strain KCTC 2194 accumulated highest PHA of 55% with a total DCW of 3.3 g/L from treated algae. By using un-treated G. amansii as a carbon source, weak growth was observed in all strains. Strains KCTC 1366 and KCTC 3007 reached DCWs of 2.0 and 1.2 g/L and PHA contents of 23 and 27%, respectively, from un-treated algae. This is the first report on PHA production from acidtreated and un-treated red algae.