Cheap Carbon Source Research Articles

Optimizing bioencapsulation of yeast cells by Aspergillus tubingensis TSIP9 and applications in bioethanol production through repeated-batch fermentation

This study aimed to immobilize yeast cells using filamentous fungi owing to a number of advantages including less chemical usage, spontaneous encapsulation, strong adhesion and biocompatibility. Filamentous fungus, Aspergillus tubingensis TSIP9 could form sphere-shape and packed pellets using either fungal fresh spores or those stored in liquid medium for 6 weeks at 4 °C. The fungus was used to immobilize yeast Saccharomyces cerevisiae FAI via adsorption and co-cultivation methods. Scanning electron microscopy images revealed that the bioencapsulated yeast cells via co-cultivation seemed to be more tightly adhered on fungal mycelia and surrounded by extracellular polymeric substances. The yeast biocapsules also exhibited higher stability and maintained their structural integrity during repeated-batch fermentation while the immobilized yeast cells by adsorption gradually degraded during their repeated uses. The bioethanol production from glucose by yeast biocapsules were in the range of 95–98 g/L with the bioethanol yield of 0.49–0.54 g-ethanol/g-consumed glucose. The yeast biocapsules could produce bioethanol well when using enzymatic hydrolysate of lignocellulosic palm waste, as alternative cheap carbon source, with the comparable bioethanol yield of 0.49 ± 0.17 g-ethanol/g-consumed glucose. The spontaneous and inter-species bioencapsulation show the perspectives as active biocatalysts with high cell retention for repeated uses.

Biotreatment of Industrial Pollutant (Carbon Dioxide) and its Role in Bioplastics Production

Polyhydroxyalkanoates (PHAs) are a class of biopolymers with characteristics resembling those of petrochemical-based plastics that have gained recent attention and a growing amount of research effort due to their environmental friendliness. Numerous bacteria, including Alcaligenes spp., Pseudomonas spp., Staphylococcus spp., and algae create (PHAs) in the presence of carbon and limiting nutrients like nitrogen, and these biopolymers can successfully replace industrial plastics. Therefore, the goal of this study is to employ carbon dioxide, an industrial pollutant emitted into the environment, as a cheap carbon source to lower production costs and remove pollution at the same time. Only three of the nine bacterial isolates utilized were able to synthesize the polymer in the presence of CO2, and the best isolate was belonging to the genus Alcaligenes after 48 hours of incubation at 30°C and pH 7, which are the optimal conditions for polymer synthesis. Bacterial growth resulted in the production of 5.2gm/l of PHA and 6.2gm/l of biomass under these conditions.

Clostridium carboxidivorans and Rhodosporidium toruloides as a platform for the valorization of carbon dioxide to microbial oils

There is growing scientific interest in oleaginous yeasts producing microbial oils as precursors of biofuels and potential substitutes for fossil fuels. Due to the high cost of substrates commonly metabolized by yeasts, volatile fatty acids (VFAs) are gaining interest as alternative cheap and sustainable carbon sources, which can be obtained from solid, liquid and gas pollutants. In this research, Rhodosporidium toruloides was proven to be able to accumulate microbial oils from VFAs obtained from the fermentation of syngas by Clostridium carboxidivorans. Using CO2 and CO as carbon sources from the syngas mixture and H2 as energy source, this acetogen produced, via the Wood-Ljungdahl pathway, a mixture of acetic, butyric and caproic acids. It was first revealed that R. toruloides exhibited minimal inhibition at concentrations below 12 g/L when exposed to a mixture of VFAs, which included acetic, butyric and even hexanoic acids. The yeast was then grown on the culture medium derived from the acetogenic fermentation of syngas. Between the two yeast strains tested of the same species, R. toruloides DSM 4444 reached a total VFAs consumption of 69.1 g/L, supplied by successive additions of acids to the reactor, yielding a maximum lipid content of 29.7% w/w cell. The lipid profile obtained in this case, in terms of abundance followed the order C18:1 > C16:0 ≥ C18:0 > C18:2>others; in which the dominant compound (C18:1), represented approximately 50% of the total. This research opens new possibilities in the cultivation of oleaginous yeasts for the production of biofuels and bioproducts from C1 gases.

Screening and fermentation of high-yield glycolic acid strains

Glycolic acid is an important chemical product widely used in various fields, including cosmetics, detergents, textiles, and more. Currently, microbial production of glycolic acid has disadvantages such as poor genetic stability, low yield, and high cost. Additionally, whole-cell catalytic production of glycolic acid typically requires the addition of relatively expensive sorbitol as a carbon source, which limits its industrial production. To develop an industrially applicable method for glycolic acid production, this study used ethylene glycol as a substrate to screen the glycolic acid-producing strains through whole-cell catalysis, obtaining a Rhodotorula sp. capable of producing glycolic acid. The strain was then subjected to UV mutagenesis and high throughput screening, and the positive mutant strain RMGly-20 was obtained. After optimization in shake flasks, the glycolic acid titer of RMGly-20 reached 17.8 g/L, a 10.1-fold increase compared to the original strain. Using glucose as the carbon source and employing a fed-batch culture in a 5 L fermenter, strain RMGly-20 produced 61.1 g/L of the glycolic acid. This achievement marks the preliminary breeding of a genetically stable glycolic acid-producing strain using a cheap carbon source, providing a new host for the biosynthesis of glycolic acid and promoting further progress toward industrial production.

Preparation of slow-release carbon source fillers from agricultural solid waste for efficient nitrogen removal from municipal wastewater: Removal performance, microbial community and mechanisms

In this study, five types of agricultural wastes, were used as alternative materials for slow-release carbon source, alternative materials were prepared as slow-release carbon source fillers (ZCF) using a no-sintering method, and studied by leaching elements, carbon release, nitrification and denitrification potential, and bio-attachment performance, walnut shell-based filler was found to have better performance in terms of persistence of carbon release, impact stability, carbon biochemistry and green safety. When HRT was 8 h in H-O, 12 h in H-A, and R was 100 % and C/N was 2 in H-Z BAF, the average concentrations of effluent NH4+-N and TN were only 0.4 and 12.2 mg/L, which achieved the high efficiency and economy of H-Z BAF under low C/N conditions. The newly prepared ZCF had a rougher outer surface, a uniformly distributed flocculent structure and numerous microporous channels on the inner surface, and the carbon source inside the filler was degraded or transformed by microorganisms, as compared to the filler in H-O and H-A at the later stage of use. The abundance of nitrifying bacteria, denitrifying bacteria was increased in the H-Z BAF, and that functional CAZymes were enriched and involved in the degradation of cellulose and hemicellulose, can be efficiently utilized by microorganisms. This study provides technical support for the development of cheap, stable and efficient slow-release carbon sources and their application in denitrification of municipal wastewater plant tailwater.

Lactic Acid: Industrial Synthesis, Microorganisms-Producers and Substrates: A Review

The article contains comprehensive information on groups of bacteria producing lactic acid, which have high metabolic activity and can be used in industrial production. In addition, an overview of the most common fermentation methods (batch, continuous, multiple), as well as cheap carbon sources: starch and cellulose-containing, industrial and food waste is provided.

Polyhydroxyalkanoate Production from Eucalyptus Bark's Enzymatic Hydrolysate.

In recent years, polyhydroxyalkanoates (PHAs) have gained notoriety because of their desirable properties that include proven biodegradability, biocompatibility, and thermal stability, which make them suitable alternatives to fossil-based polymers. However, the widespread use of PHAs is still challenging because of their production costs, which are greatly associated with the cultivation medium used for bacterial cultivation. In Portugal, one-quarter of the forest area is covered by Eucalyptus globulus wood, making its residues a cheap, abundant, and sustainable potential carbon source for biotechnological uses. In this work, eucalyptus bark was used as the sole feedstock for PHA production in a circular bioeconomic approach. Eucalyptus bark hydrolysate was obtained after enzymatic saccharification using Cellic® CTec3, resulting in a sugar-rich solution containing glucose and xylose. Although with differing performances, several bacteria were able to grow and produce PHA with distinct compositions, using the enzymatic hydrolysate as the sole carbon source. Pseudomonas citronellolis NRRL B-2504 achieved a high cellular growth rate in bioreactor assays (24.4 ± 0.15 g/L) but presented a low accumulation of a medium-chain-length PHA (mcl-PHA) comprising the monomers hydroxydecanoate (HD, 65%), hydroxydodecanoate (HDd, 25%), and hydroxytetradecanoate (HTd, 14%). Burkholderia thailandensis E264, on the other hand, reached a lower cellular growth rate (8.87 ± 0.34 g/L) but showed a higher biopolymer accumulation, with a polyhydroxybutyrate (PHB) content in the cells of 12.3 wt.%. The new isolate, Pseudomonas sp., revealed that under nitrogen availability, it was able to reach a higher accumulation of the homopolymer PHB (31 wt.%). These results, although preliminary, demonstrate the suitability of eucalyptus bark's enzymatic hydrolysate as a feedstock for PHA production, thus offering an exciting avenue for achieving sustainable and environmentally responsible plastic products from an undervalued forestry waste.

Effect of purification methods on the quality and morphology of plastic waste-derived carbon nanotubes

Recent innovative research efforts on the usage of plastic wastes as a cheap carbon source for carbon nanotubes (CNTs) production have emerged as a low-cost and sustainable means of producing CNTs. However, plastic waste-derived CNTs are rarely used in some purity-sensitive and high-alignment needed applications due to the poor quality of CNTs resulting from the abundance of impurities such as non-crystalline amorphous carbon, metallic nanoparticles, and other impurities. Therefore, purification is a crucial issue to be addressed to fully harness all potential applications of CNTs derived from waste plastic materials. Here, the effect of employing different purification methods on the morphology and purity of waste plastic-derived CNTs was investigated. CNTs were synthesized using waste polypropylene plastic as carbon feedstock via a single-stage catalytic chemical vapour deposition (CVD) technique. As-produced CNTs were purified using liquid-phase oxidation (chemical oxidation in nitric acid), gas-phase oxidation in air, and a combination of both liquid- and gas-phase oxidation methods. The synthesized and purified CNTs were characterized for morphology, purity, surface functional groups, thermal stability, and crystallinity using Transmission electron microscopy (TEM), Raman spectroscopy, Fourier Transform Infrared spectroscopy (FTIR), Thermogravimetric analysis (TGA), and X-ray diffraction (XRD), respectively. Results obtained showed that a combination of both liquid and gas phase oxidation purification techniques resulted in purer, better quality, and less defective CNTs with an IG’/IG value of 0.89 and ID/IG value of 0.86, while chemically treated CNTs (CNT-PC) presented more structurally defective CNTs and shortened nanotubes compared to other investigated treatment methods with an ID/IG value of 0.96. CNTs purified by a multi-step protocol (CNT-PAC) showed the highest weight loss of 72.3% indicating the highest quality and the presence of filamentous carbon. This study confirms that the choice of purification techniques influences the morphology and quality of plastic-derived CNTs.

Polyhydroxybutyrate (PHB) bioplastic characterization from the isolate Pseudomonas stutzeri PSB1 synthesized using potato peel feedstock to combat solid waste management

The global fossil-based plastic industry is at a crucial point, requiring bio-based polymers. Polyhydroxybutyrate (PHB) is formed under nutritional stress conditions; however, efficient bacteria and cheap substrates are needed. This study found that potato peel, a cheap and abundant carbon source, can improve PHB production. PHB crotonic assay screened 11 Sudan Black B and Nile red positive isolates for PHB production. PSB1, a Pseudomonas stutzeri PSB1 (MN539619) yields 2.39 g/L maximal PHB. PHB generation from high-carbon agro-wastes using Pseudomonas stutzeri PSB1was 3.09 g/L for potato peel. Plackett-Burman and CCD, a statistical optimization method, increased PHB production. After optimizing all CCD variables, potato peel, Urea, and RPM were found to increase PHB production (6.1 g/L). The optimized parameters extracted 3.98 g/L of PHB from 6.36 g/L of dry biomass of Pseudomonas stutzeri PSB1. FT-IR, NMR, TGA, and DSC were used to characterize and compare the extracted PHB biopolymer to Sigma Aldrich PHB powder. Extracted PHB-bioplastic was tested for tensile strength and Elongation at break. Based on the above criteria, the recovered PHB biopolymer from Pseudomonas stutzeri PSB1 is a good alternative to agricultural mulch films and non-biodegradable plastics.

Bioleaching for metals removal from mine tailings flotation fractions

This study investigated two bioleaching strategies for removing heavy metals from three mine tailings fractions generated by flotation processes. On the one hand, bioleaching with microbial consortia of acidophilic mesophiles and moderate thermophiles efficiently extracted Co, Cu, Zn, and As, while the leaching of Pb was facilitated through the use of organic acids produced by a heterotrophic bacterium and a fungus. Approximately 100% Co, 68% Zn, 63% As, and 31% Cu were bioleached with acidophilic mesophiles from the barite tailings (BT) sample after 14 days, whereas for the barite concentrate (BC) sample the results showed about 100% Co, 70% Zn and As, and 45% Cu removal at the same period. The sulfide concentrate (SC) sample underwent bioleaching with both consortia, acidophilic mesophiles and moderate thermophiles over 28 days. Approximately, 67% of Co, 28% of Zn, 56% of As, 28% of Cu, and 6% of Mn were extracted from the sample using mesophiles, whereas the leaching efficiency with the moderate thermophiles was about 72% of Co, 50% of Zn, 28% of As, 36% of Cu, and 5% of Mn in 20 L bioreactors. On the other hand, bioleaching of Pb was explored using the bacterium Gluconobacter oxydans and the fungus Penicillium simplicissimum for the production of gluconic acid and citric acid, respectively. Additionally, besides glucose-based media, glycerol and crystal sugar were tested as alternative and cheaper carbon sources. The metabolic activity of P. simplicissimum allowed a maximum Pb leaching of 39–43% from the BT sample in 28 days in glycerol-based medium, while for the BC sample, the maximum Pb extraction was around 60% in glucose-based medium. A lower extraction of Pb was achieved with G. oxydans for both samples. The maximum extraction of 34% and 39% of Pb was reached within 7 days when glucose was used as the carbon source. Further optimization should address both the enhancement of metals removal and – especially for the organic acid bioleaching – the reduction of costs related to media formulation and fungal biomass production on a larger scale.

Komagataella phaffii as a Platform for Heterologous Expression of Enzymes Used for Industry.

In the 1980s, Escherichia coli was the preferred host for heterologous protein expression owing to its capacity for rapid growth in complex media; well-studied genetics; rapid and direct transformation with foreign DNA; and easily scalable fermentation. Despite the relative ease of use of E. coli for achieving the high expression of many recombinant proteins, for some proteins, e.g., membrane proteins or proteins of eukaryotic origin, this approach can be rather ineffective. Another microorganism long-used and popular as an expression system is baker's yeast, Saccharomyces cerevisiae. In spite of a number of obvious advantages of these yeasts as host cells, there are some limitations on their use as expression systems, for example, inefficient secretion, misfolding, hyperglycosylation, and aberrant proteolytic processing of proteins. Over the past decade, nontraditional yeast species have been adapted to the role of alternative hosts for the production of recombinant proteins, e.g., Komagataella phaffii, Yarrowia lipolytica, and Schizosaccharomyces pombe. These yeast species' several physiological characteristics (that are different from those of S. cerevisiae), such as faster growth on cheap carbon sources and higher secretion capacity, make them practical alternative hosts for biotechnological purposes. Currently, the K. phaffii-based expression system is one of the most popular for the production of heterologous proteins. Along with the low secretion of endogenous proteins, K. phaffii efficiently produces and secretes heterologous proteins in high yields, thereby reducing the cost of purifying the latter. This review will discuss practical approaches and technological solutions for the efficient expression of recombinant proteins in K. phaffii, mainly based on the example of enzymes used for the feed industry.

Valorization of cantaloupe waste for green microwave-driven synthesis of N-self doped CQDs as a fluorescence sensor for nizatidine in urine and pharmaceuticals. A step ahead for circular economy practice

In the current study, a fast, ecological, one-pot, and cost-efficient method was developed for the synthesis of nitrogen-doped carbon quantum dots (N-CQDs) using plant wastes. This method includes the treatment of cantaloupe seeds and mush by microwave for four-minutes as a re-cyclable, green, and cheap carbon and nitrogen source. The furnished N-CQDs show a fluorescence quantum yield of 13.15 %, excellent water solubility, and high stability. A full characterization of the plant waste-derived quantum dots revealed the self-doping with nitrogen. The synthesized N-CQDs have been applied as an efficient nanoprobe for fluorometric determination of nizatidine (NZT), a gastroprotective drug, at λex/λem of 325/416 nm within the concentration range of 0.75–100.0 μM and LOD of 0.24 μM. The N-CQDs show excellent selectivity for NZT in the presence of various possibly co-existing substances. Excellent mean % recovery was achieved for the determination of NZT in capsules (101.97 ± 0.91 %). Moreover, the N-CQDs were used for the determination of NZT in human urine within the concentration range of 2.5–100.0 μM with LOD of 0.8 μM, therefore it has been applied for monitoring the excretion profile of NZT in urine. The greenness of the proposed probe has been evaluated using two greenness software and metrics proving excellent greenness feature that is attributed to using a renewable and cheap plant waste product as a feedstock via low-energy/low-cost microwave-assisted synthesis, elimination of organic solvents and hazardous chemicals, and relying on a direct mix-and-read assay.

Challenges and Advances in the Bioproduction of L-Cysteine.

L-cysteine is a proteogenic amino acid with many applications in the pharmaceutical, food, animal feed, and cosmetic industries. Due to safety and environmental issues in extracting L-cysteine from animal hair and feathers, the fermentative production of L-cysteine offers an attractive alternative using renewable feedstocks. Strategies to improve microbial production hosts like Pantoea ananatis, Corynebacterium glutamicum, Pseudomonas sp., and Escherichia coli are summarized. Concerning the metabolic engineering strategies, the overexpression of feedback inhibition-insensitive L-serine O-acetyltransferase and weakening the degradation of L-cysteine through the removal of L-cysteine desulfhydrases are crucial adjustments. The overexpression of L-cysteine exporters is vital to overcome the toxicity caused by intracellular accumulating L-cysteine. In addition, we compiled the process engineering aspects for the bioproduction of L-cysteine. Utilizing the energy-efficient sulfur assimilation pathway via thiosulfate, fermenting cheap carbon sources, designing scalable, fed-batch processes with individual feedings of carbon and sulfur sources, and implementing efficient purification techniques are essential for the fermentative production of L-cysteine on an industrial scale.

A DFT study of CO2 electroreduction catalyzed by hexagonal boron-nitride nanosheets with vacancy defects.

In addition to providing a sustainable route to green alternative energy and chemical supplies from a cheap and abundant carbon source, recycling CO2 offers an excellent way to reduce net anthropogenic global CO2 emissions. This can be achieved via catalysis on 2D materials. These materials are atomically thin and have unique electrical and catalytic properties compared to bigger nanoparticles and conventional bulk catalysts, opening a new arena in catalysis. This paper examines the efficacy of hexagonal boron nitride (h-BN) lattices with vacancy defects for CO2 electroreduction (CO2RR). We conducted in-depth investigations on different CO2RR electrocatalytic reaction pathways on various h-BN vacancy sites using a computational hydrogen model (CHE). It was shown that CO binds to h-BN vacancies sufficiently to ensure additional electron transfer processes, leading to higher-order reduction products. For mono-atomic defects VN (removed nitrogen), the electrochemical path of (H+ + e-) pair transfers that would lead to the formation of methanol is most favorable with a limiting potential of 1.21 V. In contrast, the reaction pathways via VB (removed boron) imposes much higher thermodynamic barriers for the formation of all relevant species. With a divacancy VBN, the hydrogen evolution reaction (HER) would be the most probable process due to the low rate-determining barrier of 0.69 eV. On the tetravacancy defects VB3N the pathways toward the formation of both CH4 and CH3OH impose a limiting potential of 0.85 V. At the same time, the HER is suppressed by requiring much higher energy (2.15 eV). Modeling the edges of h-BN reveals that N-terminated zigzag conformation would impose the same limiting potential for the formation of methanol and methane (1.73 V), simultaneously suppressing the HER (3.47 V). At variance, the armchair conformation favors the HER, with a rate-determining barrier of 1.70 eV. Hence, according to our calculations, VB3N and VN are the most appropriate vacancy defects for catalyzing CO2 electroreduction reactions.

SO3H‐Functionalized Carbon Materials: A Versatile and sustainable heterogeneous Catalyst for Diverse Organic Transformations

AbstractDue to their fascinating biological features, heterocyclic compounds and their derivatives have long been recognized as promising molecules with potential pharmaceutical applications. The significance of heterocyclic compounds in drug discovery and development is evident from the fact that a majority of drugs in the pharmaceutical market incorporate heterocyclic compounds as active substances or ingredients. Various synthetic methods and advancements have been devised to prepare these heterocyclic compounds using diverse catalysts under mild reaction conditions. SO3H functionalized carbon material (C‐SO3H) is heterogeneous green solid catalyst that has been employed to catalyze diverse organic reactions including construction of three‐, four‐, five‐, six‐member and fused heterocycles as well as other open chain organic transformations. The C‐SO3H catalyst works under relatively mild reaction conditions and recovered from the reaction mixtures for reuse. Various cheap carbon sources covering natural organic carbon matter and industrial waste already being used to synthesize SO3H‐functionalized acidic carbon catalyst for replacement of various homogeneous acid catalysts. The present review aims to highlight the organic reactions especially those connecting for heterocyclic synthesis catalyzed by sulfonated carbons (C‐SO3H) from 2010 to till date.

A Green Approach to Obtaining Glycerol Carbonate by Urea Glycerolysis Using Carbon-Supported Metal Oxide Catalysts.

The results of sustainable and selective synthesis of glycerol carbonate (GC) from urea and glycerol under ambient pressure using carbon-fiber-supported metal oxide catalysts are reported. Carbon fibers (CF) were prepared via a catalytic chemical vapor deposition method (CCVD) using Ni as a catalyst and liquefied petroleum gas (LPG) as a cheap carbon source. Supported metal oxide catalysts were obtained by an incipient wetness impregnation technique using Zn, Ba, Cr, and Mg nitrates. Finally, the samples were pyrolyzed and oxidized in an air flow. The obtained catalysts (10%MexOy/CFox) were tested in the reaction of urea glycerolysis at 140 °C for 6 h under atmospheric pressure, using an equimolar ratio of reagents and an inert gas flow for NH3 removal. Under the applied conditions, all of the prepared catalysts increased the glycerol conversion and glycerol carbonate yield compared to the blank test, and the best catalytic performance was shown by the CFox-supported ZnO and MgO systems. Screening of the reaction conditions was carried out by applying ZnO/CFox as a catalyst and considering the effect of reaction temperature, molar ratio of reagents, and the mode of the inert gas flow through the reactor on the catalytic process. Finally, a maximum yield of GC of about 40%, together with a selectivity to glycerol carbonate of ~100%, was obtained within 6 h of reaction at 140 °C using a glycerol-to-urea molar ratio of 1:1 while flowing Ar through the reaction mixture. Furthermore, a positive heterogeneous catalytic effect of the CFox support on the process was noticed.

Polyhydroxybutyrate (PHB) production from sugar cane molasses and tap water without sterilization using novel strain, Priestia sp. YH4

The production cost of biodegradable polymer like polyhydroxybutyrate (PHB) is still higher than that of petroleum-based plastics. A potential solution for reducing its production cost is using a cheap carbon source and avoiding a process of sterilization. In this study, a novel PHB-producing microbial strain, Priestia sp. YH4 was screened from the marine environment using sugarcane molasses as the carbon source without sterilization. Culture conditions, such as carbon, NaCl, temperature, pH, inoculum size, and cultivation time, were optimized for obtaining the highest PHB production by YH4 resulting in 5.94 g/L of dry cell weight (DCW) and 61.7 % of PHB content in the 5 mL culture. In addition, it showed similar PHB production between the cultures with or without sterilization in Marine Broth media. When cultured using only tap water, sugarcane molasses, and NaCl in a 5 L fermenter, 24.8 g/L DCW was produced at 41 h yielding 13.9 g/L PHB. Finally, DSC (Differential Scanning Calorimetry) and GPC (Gel Permeation Chromatography) were used to analyze thermal properties and molecular weights resulting in Tm = 167.2 °C, Tc = 67.3 °C, Mw = 2.85 × 105, Mn = 1.05 × 105, and PDI = 2.7, respectively. Therefore, we showed the feasibility of more economical process for PHB production by finding novel strain, utilizing molasses with minimal media components and avoiding sterilization.

Valorisation of Pineapple Cannery Waste as a Cost Effective Carbon Source for Poly 3-hydroxyabutyrate (P3HB) Production.

Pineapple is one of the most important agro-industrial sugar-based fruits in Thailand. In this study, the waste stream from pineapple cannery processing was utilised and evaluated for potential use in the production of a main biopolymer group widely known as polyhydroxyalkanoates (PHAs) through aerobic batch fermentation. Firstly, pineapple cannery waste (PCW) collected from three processing sources, pineapple juice (PAJ), peel and core juice (PCJ), and pulp-washing water (PWW), was used as a carbon source. Secondly, it was characterised and pretreated. Then, batch fermentation was performed by using the optimal condition (200 rpm agitation rate, 37 °C, and fermentation time of 72 h) under two different nutrient conditions in each type of carbon source. The results revealed that PHAs were produced during 24-72 h of fermentation without any interference. The PHAs product obtained was characterised by their properties. Interestingly, GC-MS showed homopolymer of poly 3-hydroxybutyrate (P3HB) group characteristics, such as OH, CH, and C=O; meanwhile, H1 NMR analysis showed signals corresponding to CH3, CH2, and CH, respectively. Remarkably, utilising the PCW showed a high-potential cheap carbon source for the production of PHAs as well as for the treatment of wastewater from the fruit industry.

Alanine dehydrogenases from four different microorganisms: characterization and their application in L-alanine production

BackgroundAlanine dehydrogenase (AlaDH) belongs to oxidoreductases, and it exists in several different bacteria species and plays a key role in microbial carbon and nitrogen metabolism, spore formation and photosynthesis. In addition, AlaDH can also be applied in biosynthesis of L-alanine from cheap carbon source, such as glucose.ResultsTo achieve a better performance of L-alanine accumulation, system evaluation and comparison of different AlaDH with potential application value are essential. In this study, enzymatic properties of AlaDH from Bacillus subtilis 168 (BsAlaDH), Bacillus cereus (BcAlaDH), Mycobacterium smegmatis MC2 155 (MsAlaDH) and Geobacillus stearothermophilus (GsAlaDH) were firstly carefully investigated. Four different AlaDHs have few similarities in optimum temperature and optimum pH, while they also exhibited significant differences in enzyme activity, substrate affinity and enzymatic reaction rate. The wild E. coli BL21 with these four AlaDHs could produce 7.19 g/L, 7.81 g/L, 6.39 g/L and 6.52 g/L of L-alanine from 20 g/L glucose, respectively. To further increase the L-alanine titer, competitive pathways for L-alanine synthesis were completely blocked in E. coli. The final strain M-6 could produce 80.46 g/L of L-alanine with a yield of 1.02 g/g glucose after 63 h fed-batch fermentation, representing the highest yield for microbial L-alanine production.ConclusionsEnzyme assay, biochemical characterization and structure analysis of BsAlaDH, BcAlaDH, MsAlaDH and GsAlaDH were carried out. In addition, application potential of these four AlaDHs in L-alanine productions were explored. The strategies here can be applied for developing L-alanine producing strains with high titers.

A novel design idea of high-stability silicon anodes for lithium-ion batteries: Building in-situ “high-speed channels” while reserving space

As one of the most promising anode materials for high-performance lithium-ion batteries, the commercial application of Si faces many dilemmas. In this paper, a facile method is developed to substantially improve the cycling stability of Si-based anodes. Firstly, based on the Kirkendall effect, the Si nanoparticle was transformed into multi-Si-void@SiO2 by heat-treatment. Then, the acid precipitation process was used to coat the lignin on the surface of the multi-Si-void@SiO2 structure via the hydrogen-bond interaction, and after in-situ carbonization, multi-Si-void@SiO2@lignin-based carbon composite was formed. The optimum electrode material maintained the specific capacity of 759 mA h g−1 after 1300 cycles at the current density of 1.0 A/g. The great electrochemical performance is attributed to the four components of voids, Si, SiO2 and lignin-based carbon (LC) performing their duties and synergistically, making the electrode exhibit excellent cycle stability. After long-term charge/discharge process, SiO2 layer is fully activated to construct Li4SiO4 and Li2O “high-speed channels”, providing a “bridge” for Si to connect with the outside. And the reserved space inside the structure is conducive to the free expansion and contraction of Si. Meanwhile, lignin, as a cheap and renewable carbon source, greatly reduces the cost of material preparation. Consequently, the multi-Si-void@SiO2@LC composite presented here provides a feasible strategy for the large-scale development of highly stable Si-based anodes.