Additional Carbon Source Research Articles

Immobilization of Zn and Cu in Conditions of Reduced C/N Ratio during Sewage Sludge Composting Process

In this paper we present results of research on the transformation of chemical forms of two elements (Cu, Zn) that occurred at the highest concentration in sewage sludge being processed in a composting process. The factor that had impact on the direction of the observed transformation was the amount of straw added to the mix with sewage sludge at the batch preparation stage including elimination of an additional source of organic carbon (straw). The analysis of contents of Cu and Zn chemical forms was performed applying Tessiere’s methodology. It was ascertained that reduction of supplementation has positive impact on the allocation of tested elements in organic (IV) and residual (V) fractions with a simultaneous decrease of heavy metals mobile forms share in bioavailable fractions, mostly ion exchangeable (I) and carbonate (II). Using an artificial neural network (ANN), a tool was developed to classify composts based on Austrian standards taking into account only I ÷ IV fractions treated as a labile, potentially bioavailable, part of heavy metals bound in various chemical forms in compost. The independent variables that were predictors in the ANN model were the composting time, C/N, and total content of the given element (total Cu, Zn). The sensitivity coefficients for three applied predictors varied around 1, which proves their significant impact on the final result. Correctness of the predictions of the generated network featuring an MLP 3-5-3 structure for the test set was 100%.

Systematical δ13C investigations of TOC in aquatic plants, DIC and dissolved CO2 in lake water from three Tibetan Plateau lakes

The carbon isotope values (δ13C) of aquatic plants are of great significance for recognizing carbon cycles and tracing environmental changes in lakes. Yet, the influence of δ13C values of their utilizing carbon sources (especially in the case of CO2 separated from the HCO3– in water) on their δ13C differences have never been evaluated, which is mainly due to the lack of CO2 δ13C investigations in lake water. In this study, we used a newly developed fast-response automated gas equilibrator for real-time concentration and δ13C determination of dissolved CO2 in the surface and bottom lake water of Lake Tuosu, Lake Qinghai and Lake Keluke, China. Moreover, we determined the corresponding δ13C values of total organic carbon (TOC) of a submerged plant (Potamogeton) and an alga (Cladophora), as well as the δ13C values of dissolved inorganic carbon (DIC) in bottom lake water. The results showed that the CO2 δ13C values of bottom and surface water in these three lakes did not show significant differences and the δ13C values of CO2 at different water depths also did not show significant differences. However, Potamogeton had higher TOC δ13C values (average 14–16‰) than Cladophora in these lakes. Although Potamogeton and Cladophora could utilize HCO3– as an additional carbon source whose δ13C values were more positive (ca. 7–8‰) than CO2, this effect on their δ13C values was no >4‰ after evaluation. Thus, our results show that the δ13C values of carbon sources (including CO2 and HCO3–) are not the main factors in determining the TOC δ13C difference between Potamogeton and Cladophora, which could be primarily related to the biosynthetic fractionation for different aquatic plant species. Our results benefit further understanding and interpretations of δ13C variations in carbon cycles and paleoenvironment reconstructions for lakes.

Intermittent Microaeration Technology to Enhance the Carbon Source Release of Particulate Organic Matter in Domestic Sewage

Domestic sewage treatment plants often have insufficient carbon sources in the influent water. To solve this problem, the commonly used technical means include an additional carbon source, primary sludge fermentation, and excess sludge fermentation, but these methods are uneconomical, unsustainable, and not applicable to small-scale wastewater treatment plants. Intermittent microaeration technology has the advantages of low energy-consumption, ease of application, and low cost, and can effectively promote anaerobic digestion of municipal sludge; however little research has been reported on its use to enhance the carbon sources release of particulate organic matter (POM) from domestic wastewater. Therefore, the effect of intermittent microaeration on the carbon source release of POM was evaluated in this study, with POM as the control test. The results showed that the release concentration of soluble chemical oxygen demand (SCOD) was the highest on day 4 under microaerobic conditions, and the concentrations of SCOD, NH4+-N, and PO43−-P in the liquid phase were 1153, 137.1, and 13 mg/L, respectively. Compared with the control group, the SCOD concentration increased by 34.2%, and the NH4+-N and PO43−-P concentrations decreased by 18.65% and 17.09%, respectively. Intermittent microaeration can effectively promote the growth of Paludibacter, Actinomyces, and Trichococcus hydrolytic fermentation functional bacteria. Their relative abundances increased by 282.83%, 21.77%, and 23.47%, respectively, compared with the control group. It can simultaneously inhibit the growth of acetate-type methanogenic archaea, Methanosaeta and Methanosarcina, with a decrease in relative abundances of 16.81% and 6.63%, respectively. The aforementioned data show that intermittent microaeration can not only promote the hydrolysis of POM, but can also reduce the loss of acetic acid carbon source, which is a cost-effective technical way to enhance the release of a carbon source of particulate organic matter in domestic sewage.

Controlling Water Quality through a Biofloc Technology (BFT) in Aquaculture Production Systems

Information on dynamics of water quality is essential in fish rearing. The use of biofloc technology (BFT) improves fish production in regions with low water availability. This study was carried out to evaluate the use of locally available carbon sources to control total ammonia nitrogen and other water quality parameters in aquaculture production system. Completely randomized design was carried out with three different carbon sources (wheat flour, rice bran and molasses) and four different treatments [wheat flour (WF), rice bran (RB), molasses (MOL) and rice bran and molasses mix in 1:1 ratio (MIX)]. Each treatments had three replicates. Control tanks were maintained excluding additional carbon sources. Carbon to Nitrogen ratio was 10:1.The experiment was carried out in 80 L, fiber glass (15) tanks with indoor conditions for 60 days. A number of 30 male guppy (Poecilia reticulate) individuals were stocked in each tank (mean weight 0.1481±0.0500 g and standard length 1.8±0.2 cm). Water quality parameters; pH, dissolved oxygen (DO) and temperature were measured on daily basis. Total ammonium nitrogen, nitrite and nitrate were measured on weekly basis. The total ammonium nitrogen in the control (1.1746±0.1709 mg/L) was significantly higher than the biofloc treatments (p<0.05). Control (0.0897±0.0374) and wheat flour treatment (0.0939±0.0152) showed a significantly higher nitrite values than other BFT treatments (p<0.05). Nitrate in control (1.1871±0.1331) and wheat flour (0.3779±0.1044) treatment showed a significantly high values than other BFT treatments (p<0.05). DO, pH and temperature variation was similar among the BFT groups (p>0.05). Overall results indicated that there is a significant effect which led to a paramount balance of standard water quality in aquaculture production system through different carbon sources (ricebran, molasses and ricebran:molasses mix) based biofloc system. Keywords: Water quality, Carbon sources, Carbon ratio, Total ammonium nitrogen, Aquaculture production systems

Effect of carbon source conditions on response of nitrifying sludge to 3,5-dichlorophenol

Nutritional conditions of activated sludge had a significant influence on nitrification inhibition response. This study comprehensively investigated the inhibition of 3,5-dichlorophenol (3,5-DCP) on nitrification of activated sludge with different C/N ratios and carbon source types. The corresponding extracellular polymeric substances (EPS), microbial communities and functional genes were analysed. The results indicated that the addition of carbon source would reduce the nitrification activity and nitrification sensitivity to 3,5-DCP, and the order of the EC50 was sequenced as sodium acetate > methanol > glucose. The response mechanisms of activated sludge under diverse carbon source conditions to 3,5-DCP were summarised as follows. When the 3,5-DCP content was increased from 0.4 mg/L to 0.8 mg/L, the protein content increased from 73.2 ± 2.6 mg/g SS ∼122.4 ± 4 mg/g SS to 92.2 ± 11.2 mg/g SS ∼130.8 ± 9.6 mg/g SS in the tightly bound EPS (TB-EPS). The increase of protein content was attributed to cellular self-protection mechanisms. Furthermore, fluorescence characteristic analysis revealed that tyrosine and tryptophan in loosely bound EPS (LB-EPS) might account for higher EC50 in activated sludge fed with methanol and sodium acetate. In addition, the redundancy analyses (RDA) showed activated sludge with organics enriched the resistant species, such as Proteobacteria and Patescibacteria, while activated sludge without organics enriched the sensitive species, such as Ferruginibacter. Finally, the nitrification genes were found to be consistent with nitrification activity. Thus, the findings provide new insights into nitrification inhibition mechanism under different carbon source conditions.

New chemical pathway for large-area deposition of doped diamond films by linear antenna microwave plasma chemical vapor deposition

Today, boron-doped diamond (BDD) is among the key materials for electrochemical sensing and advanced oxidation of micropollutants. Therefore, a cost-effective fabrication of large-area BDD electrodes is of high interest. We present an implementation of a liquid-phase boron precursor trimethyl borate for large-area deposition of boron-doped diamond films by linear antenna microwave plasma CVD. Trimethyl borate vapors were used not only as a source of boron for doping but also as the only source of carbon and oxygen, while completely saturating the requirements for the growth of high-quality boron-doped diamond films. However, to allow for control over the doping level through maintaining the B/C and B/O ratios, carbon dioxide was employed as an additional source of carbon and oxygen. The film morphology was controllable from microcrystalline to ultra-nanocrystalline by changing the concentrations of trimethyl borate. Using this unique precursor system, we were able to grow diamond films with a doping level in range from 8 × 1017 cm−3 to 2 × 1022 cm−3 and resistivity as low as 1.16 × 10−2 Ω·cm. Low activation energies were calculated from the Arrhenius plot and growth rates as high as up to 170 nm/h for the low pressure microwave plasma CVD were reached. The investigation of the plasma emission spectrum revealed a chemical composition similar to that of hydrogen-rich plasmas with methane, and the proposed chemical reactions indicate that the diamond growth takes place via the hydroxyl radical. The results demonstrated that trimethyl borate is a suitable source of carbon and boron for the large-area growth of highly boron-doped diamond via low pressure microwave plasma CVD methods.

In-situ growth of iron nanoparticles on porous carbon nanofibers for structural high-performance lithium metal anode

Lithium metal anodes have attracted increasing attention in recent years. However, there are still significant challenges in the electrochemical cycle of lithium metals, including the growth of lithium dendrites, the formation of "dead lithium" layers, and unrestricted volume expansion. To solve these problems, using inexpensive acetylacetonate salt, polyacrylonitrile, and polymethyl methacrylate as raw materials, a 3D porous carbon nanofiber scaffold decorated with iron nanoparticles is reasonably designed by novel and unique in-situ growth method, without hazardous atmosphere, expensive catalyst deposition, and additional carbon sources. Notably, the obtained iron-doped 3D porous fibers can be used as lithium metal anode framework with low lithium deposition overpotential and long cycling stability under various current densities. The porous host structure can adapt to the inherent volume expansion and the transmission of lithium ions in the process of lithium plating/stripping, thereby improving the cycling stability. Density functional theory calculations indicate that carbon nanofibers decorated with Fe nanoparticles are more likely to absorb lithium atoms, resulting in more uniform lithium deposition. The present work provides a low-cost and scalable strategy for constructing 3D structural high-efficiency lithium metal anode, and opens new horizons for the research of lithium metal batteries and even other metal batteries.

Effects of applying different carbon substrates on nutrient removal and greenhouse gas emissions by constructed wetlands treating carbon-depleted hydroponic wastewater

The addition of external carbon sources is crucial for effective biological treatment of nutrient-rich but carbon-depleted hydroponic wastewater using constructed wetlands. In this study, we examined the effects of applying three types of carbon substrates, namely sucrose, hydroponic kale residues, and common reed litter, on the nutrient removal efficiency and greenhouse gas emission rate of vertical flow constructed wetlands. The addition of sucrose and common reed litter was shown to perform equally well in enhancing the removal of total nitrogen (84.9–93.5%), nitrate (98.3–99.8%) and phosphate (53.8–55.2%) as compared to the control. Moreover, the application of common reed litter led to significantly lower mean CH4 and N2O emissions than that of kale residues. These findings suggested that Phragmites reed litter, which is easily found in wetlands worldwide, could be an effective, low-cost and climate-friendly carbon substrate to be applied in constructed wetlands for hydroponic wastewater treatment.

Effect of Distillery Spent Wash at Different C/N Ratio on Biofloc based Nursery Culture of Penaeus vannamei

Background: Biofloc technology is one of the methods to overcome the problems associated with high ammonia-nitrogen and nitrate-nitrogen concentration in the water. The addition of carbon source is one of the practical ways to increase the C/N ratio and to promote the floc development in the culture system. The present research was carried out to assess the effect of distillery spent wash (DSW) at different C/N ratios on floc formation and growth of the shrimp under an intensive culture system. Methods: A 35-day experiment was conducted to study the effect of DSW at different C/N ratios (10, 15, 20 and 25) on the development of biofloc in the nursery culture of Penaeus vannamei. Floc development, water quality and growth performance of P. vannamei were also studied. Result: It was observed that significantly (p less than 0.05) higher specific growth rate (12.03±0.15), survival, final weight gain and better feed conversion ratio (1.25±0.02) of the shrimp at C/N 15 treatment. The study also recorded an increase in C/N ratio decreases the growth performance of the shrimp. The present study reported that, in a DSW based biofloc system, C/N ratio of 15 showed a positive effect on water quality parameters, survival and enhanced growth of cultured shrimp.

Continuous Bioleaching of Arsenic-Containing Copper-Zinc Concentrate and Shift of Microbial Population under Various Conditions

The goal of this work was to study the bioleaching of arsenic-containing polymetallic concentrate that contained 6.2% Cu, 7.3% Zn and 1.7% As, depending on different temperatures and in the presence of CO2 and molasses in the medium, as well as the difference in the composition of microbial population formed under various conditions. A mixed population of moderately thermophilic and thermotolerant acidophilic microorganisms formed during the continuous bioleaching of copper concentrate was used as an inoculum. The experiments were carried out in a continuous mode in laboratory scale reactors, with a temperature range of 40 °C to 60 °C. To assess the effect of CO2 and molasses on metal leaching and microbial population composition, the experiments were carried out in three reactors: CO2 (~0.01 L/min) was supplied into the first reactor; 0.02% molasses were added to the pulp of the second reactor; and no additional carbon sources were supplied into the control reactor. The highest copper recovery (27%) was achieved at 50°C in the experiment with molasses, while the highest zinc recovery (82.1%) was reached at 45°C in the control experiment. Additional carbon sources affected the extraction of non-ferrous metals only at 60 °C and increased the extraction of copper and zinc by 12.6% and 24.2%, respectively. Both the temperature and carbon source used affected the microbial population composition. The main microbial genera revealed in the populations by next generation sequencing (NGS) were bacteria of the genera Sulfobacillus and Acidithiobacillus, as well as archaea of the genera Ferroplasma, Acidiplasma, and Cuniculiplasma. At low temperatures (40 and 45 °C), Acidithiobacillus, Sulfobacillus, and Ferroplasma predominated, while at temperatures 50–55 °C, the decrease in relative abundance of these genera occurred, and the predominance of Acidiplasma archaea was observed. The usage of both CO2 and molasses led to the increase in Sulfobacillus and Acidiplasma in relative abundance.

Self-sufficient whole-cell biocatalysis for 3-(aminomethyl) pyridine synthesis

3-(Aminomethyl) pyridine (3-AMP) is a versatile compound for the synthesis of pharmaceuticals, agricultural chemicals and numerous polymers. Efficient and mild biocatalytic synthesis is often an excellent supplement to traditional chemical synthesis methods. However, there has been no report of biocatalytic 3-AMP synthesis. In this paper, 3-AMP was synthesized for the first time by using biocatalysts co-expressing carboxylic acid reductase from Neurospora crassa (ncCAR) and ω-transaminase from Ochrobactrum anthropi (OATA) in one pot. In addition, the metabolic pathway was optimized by knocking out the transcriptional dual regulator arcA, which resulted in a 90% increase in the yield of 3-AMP. Furthermore, efficient self-sufficient whole-cell bioconversion was established by optimization, achieving 93% yield and a 40.6 mM (4.4 g/L) titer of 3-AMP without additional carbon sources. This whole-cell bioconversion system was also suitable for the high-efficiency biocatalytic synthesis of other aromatic or heterocyclic primary amines, such as benzylamine, 2-furfurylamine, 4-fluorobenzylamine, 2,4-difluorobenzylamine and 2-(aminomethyl) pyridine.Being entirely biocatalytic, our one-pot procedure provides considerable advantages in terms of economic, environmental and safety impacts over reported chemical methods.

Modelling the effect of SMP production and external carbon addition on S-driven autotrophic denitrification

The aim of this study was to develop a mathematical model to assess the effect of soluble microbial products production and external carbon source addition on the performance of a sulfur-driven autotrophic denitrification (SdAD) process. During SdAD, the growth of autotrophic biomass (AUT) was accompanied by the proliferation of heterotrophic biomass mainly consisting of heterotrophic denitrifiers (HD) and sulfate-reducing bacteria (SRB), which are able to grow on both the SMP derived from the microbial activities and on an external carbon source. The process was supposed to occur in a sequencing batch reactor to investigate the effects of the COD injection on both heterotrophic species and to enhance the production and consumption of SMP. The mathematical model was built on mass balance considerations and consists of a system of nonlinear impulsive differential equations, which have been solved numerically. Different simulation scenarios have been investigated by varying the main operational parameters: cycle duration, day of COD injection and quantity of COD injected. For cycle durations of more than 15 days and a COD injection after the half-cycle duration, SdAD represents the prevailing process and the SRB represent the main heterotrophic family. For shorter cycle duration and COD injections earlier than the middle of the cycle, the same performance can be achieved increasing the quantity of COD added, which results in an increased activity of HD. In all the performed simulation even in the case of COD addition, AUT remain the prevailing microbial family in the reactor.

Over 1000-Fold Synergistic Boost in Viniferin Levels by Elicitation of Vitis vinifera cv. Gamay Red Cell Cultures over Accumulating Phenylalanine.

Elicitation treatments of grape cell cultures with methyl jasmonate (MeJA), ultraviolet-C (UV-C) irradiation, and sucrose induce mild production of stilbenes and flavonoids due to limited substrate availability. However, these treatments cause a synergistic boost of stilbenes production when applied to two phenylalanine (Phe)-enriched transgenic grape cell lines, AroG* + STS and AroG* + FLS. The combined treatment of UV-C elicitation on the Phe-fed AroG* + STS line resulted in the highest content of stilbenes (37.8-fold increase, 17.39 mg/g dry weight (DW)) mainly due to resveratrol (64-fold, 3.23 mg/g DW) and viniferin (1343-fold, 13.43 mg/g DW). The synergistic increase following either UV-C or MeJA elicitation was due to the induction of stilbene-related genes, while sucrose treatment had no effect on gene expression levels and served as an additional carbon source for phenylpropanoids. The combined strategy presented may enable future usage of grape cell cultures for the production of stilbenes and in particular viniferin.

Fermentation liquid as a carbon source for wastewater nitrogen removal reduced nitrogenous disinfection byproduct formation potentials of the effluent

Sludge alkaline fermentation liquid (SAFL) is an alternative to sodium acetate (NaAc) in enhancing wastewater nitrogen removal. Upon SAFL addition, dissolved organic nitrogen (DON) can be externally introduced or biologically synthesized during nitrogen removal, which is an important precursor to toxic nitrogenous disinfection by-products (N-DBPs). This study aims to evaluate the effects of different carbon source addition on effluent DON concentration, composition, and N-DBP formation potentials. A lab-scale A2O system treating real municipal wastewater was operated with NaAc or SAFL as external carbon sources. DON molecules and potential N-DBP precursors were identified by Orbitrap mass spectrometry. Subsequently, major microorganisms contributing to DON biosynthesis were suggested based on metagenomics. It was found that effluent DON was higher with SAFL as the carbon source than NaAc (1.51 ± 0.24 v.s. 0.56 ± 0.08 mg N/L, p < 0.05). Nevertheless, dichloroacetonitrile and nitrosamine formation potentials (7.14 ± 1.02 and 1.57 ± 0.07 μg/mg DON-N, respectively) of the effluent with SAFL addition were 42.79 ± 2.42% and 54.89 ± 1.70% lower than those of NaAc. Protein- and lignin-like compounds were the most abundant DON molecules in the effluent, where alanine, glycine and tyrosine were important precursors to N-DBPs. Azonexus and Flavobacterium spp. were positively correlated with these precursors, and possessed key genes involved in precursor synthesis. SAFL is a promising carbon source, not only for achieving efficient inorganic nitrogen and DON removals, but also for reducing N-DBP formation potentials of chlorinated effluent.

A novel partial denitrification, anammox-biological phosphorus removal, fermentation and partial nitrification (PDA-PFPN) process for real domestic wastewater and waste activated sludge treatment

A novel process was developed for real domestic wastewater and waste activated sludge (WAS) treatment based on partial denitrification, anammox-biological phosphorus removal, fermentation and partial nitrification (PDA-PFPN). After 246 days of operation, the effluent concentrations of NH4+-N, NO2−-N and NO3−-N were below detection limits (0.1 mg/L), and the effluent concentration of PO43−-P was 0.1 mg/L without the addition of external carbon source in PDA-PFPN system. Moreover, the sludge reduction efficiency reached 48.1% due to fermentation. The nitrite accumulation ratios by ammonia oxidation and nitrate reduction pathway were 60.6% and 87%, respectively. Intracellular metabolites measured by liquid chromatography mass spectrometer (LC-MS/MS) suggested that different intracellular amino acids were stored and consumed at different duration, and intracellular Valine, Glycine and Lysine were not utilized in oxic stage. Results of flow cytometry showed that the proportion of intact cells decreased from 94.7% to 82.9%, and necrotic cells increased from 5.3% to 17.1% with the increase of DNA content in sludge supernatant and cell decay rate, indicating the occurrence of cell death and lysis and leading to WAS reduction. Analysis of transcriptional community composition revealed that partial denitrification bacteria (Thauera), anammox bacteria (Candidatus Brocadia and Candidatus Kuenenia), simultaneous phosphorus removal and fermentation bacteria (Tetrasphaera) and partial nitrification bacteria (Nitrosomonas) coexisted and actually worked in PDA-PFPN system. The novel PDA-PFPN process simultaneously achieved highly efficient nitrogen and phosphorus removal and WAS reduction without the addition of external carbon source, which greatly reduced the operation cost of carbon source dosing and WAS treatment in wastewater treatment.

Fermented Spirulina products with Saccharomyces and non- Saccharomyces yeasts: Special reference to their microbial, physico-chemical and sensory characterizations

Innovative products produced from various sources through fermentation processes have been a resurgence of interest. This study was designed to determine the performance of fermented Spirulina (FS) products by three different yeast species including Debaryomyces hansenii, Kluyveromyces marxianus and Saccharomyces cerevisiae and investigate the microbial, physicochemical and sensory characteristics of products. The results showed that the increase in yeast cell number was around 3 log after 48 h fermentation in Spirulina medium without additional carbon source. Protein bands with a molecular weight of ∼51 kDa seemed less visible and bands 14–22 kDa disappeared after 48 h fermentation by K. marxianus showed strong hydrolysis of proteins during fermentation. The amino acid compositions of the three kinds of FS were different also compared to unfermented Spirulina (unFS). Glutamic acid, methionine, lysine, isoleucine and valine became more dominant in FS samples. According to GC–MS analysis, there was a decrease in the concentration of pyrazine, ketone and aldehyde compounds of FS compared to unFS. The flavor notes of “seaweed”, “cardboard”, “earthy/muddy” and “cereal/straw” were found to be the highest in unFS than in FS detected by panelists during sensory evaluations. FS by K. marxianus is highly characterized as having the lowest “seaweed” and “umami” flavor attributes and higher “fermented” and “rose” attributes. Finally, the current study revealed that the potential of Spirulina biomass to be a suitable substrate for yeasts and fermentation of Spirulina with different yeast species led to different kinds of products.

Establishing Mixotrophic Growth of Cupriavidus necator H16 on CO2 and Volatile Fatty Acids

The facultative chemolithoautotroph Cupriavidus necator H16 is able to grow aerobically either with organic substrates or H2 and CO2 s and it can accumulate large amounts of (up to 90%) poly (3-hydroxybutyrate), a polyhydroxyalkanoate (PHA) biopolymer. The ability of this organism to co-utilize volatile fatty acids (VFAs) and CO2 as sources of carbon under mixotrophic growth conditions was investigated and PHA production was monitored. PHA accumulation was assessed under aerobic conditions, with either individual VFAs or in mixtures, under three different conditions—with CO2 as additional carbon source, without CO2 and with CO2 and H2 as additional sources of carbon and energy. VFAs utilisation rates were slower in the presence of CO2. PHA production was significantly higher when cultures were grown mixotrophically and with H2 as an additional energy source compared to heterotrophic or mixotrophic growth conditions, without H2. Furthermore, a two-step VFA feeding regime was found to be the most effective method for PHA accumulation. It was used for PHA production mixotrophically using CO2, H2 and VFA mixture derived from an anaerobic digestor (AD). The data obtained demonstrated that process parameters need to be carefully monitored to avoid VFA toxicity and low product accumulation.

Novel Poly(butylene adipate-co-terephthalate)-degrading Bacillus sp. JY35 from wastewater sludge and its broad degradation of various bioplastics

Poly(butylene adipate-co-terephthalate) (PBAT), a bioplastic consisting of aliphatic hydrocarbons and aromatic hydrocarbons, was developed to overcome the shortcomings of aliphatic and aromatic polyesters. Many studies report the use of PBAT as a blending material for improving properties of other bioplastics. However, there are few studies on microorganisms that degrade PBAT. We found six kinds of PBAT-degrading microorganisms from various soils. Among these, Bacillus sp. JY35 showed superior PBAT degradability and robustness to temperature. We monitored the degradation of PBAT films by Bacillus sp. JY35 using scanning electron microscopy, field emission scanning electron microscopy, Fourier-transform infrared spectroscopy, and gel permeation chromatography. GC-MS was used to measure the PBAT film degradation rate at different temperatures and with additional NaCl and carbon sources. Certain additional carbon sources improve the growth of Bacillus sp. JY35. However, this did not increase PBAT film degradation. Time-dependent PBAT film degradation rates were measured during three weeks of cultivation, after which the strain achieved almost 50% degradation. Additionally, various bioplastics were applied to solid cultures to confirm the biodegradation range of Bacillus sp. JY35, which can degrade not only PBAT but also PBS, PCL, PLA, PHB, P(3HB-co-4HB), P(3HB-co-3HV), P(3HB-co-3HHx), and P(3HB-co-3HV-co-3HHx), suggesting its usability as a superior bioplastic degrader.

Nutrient acclimation in benthic diatoms with adaptive laboratory evolution

The growth of marine diatom algaeChaetoceros gracilisandThalassiosira weissflogiiin agricultural fertilizers and additional carbon sources were evaluated. The main objective behind the study was to increase the growth and productivity of the diatom acclimatized under adaptive laboratory culture conditions. In optimized conditions,C.gracilisshowed the highest cell density in NPK (202.5 ± 2.6 × 105 cells mL−1), maximum carbohydrate (212.8 ± 4.0 mg g−1) and protein (133.9 ± 1.5 mg g−1) in urea. In contrast,T.weissflogiishowed the highest cell density in glycerol (148.2 ± 2.5x105 cells mL−1), maximum carbohydrate in glycerol (273.7 ± 3.3 mg g−1), and protein in sucrose (126.2 ± 0.7 mg g−1). Lipid content was maximum in glycerol (73.4 ± 0.6%) and glucose (39.7 ± 0.2%) in C. gracilisand T. weissflogii respectively. Increased pigment production and chrysolaminarin concentration were obtained in both marine species. The study highlights the importance of adaptive laboratory evolution as an promising tool in enhancing productivity in diatom algae.

Optimization of Medium Composition for Streptomyces sp. PB2 Chitinase Production using Response Surface Methodology

Highlight ResearchThe chitinase production by Streptomyces sp. PB2 was studiedThe critical medium component for chitinase production were identifiedThe optimum medium composition for chitinase production was obtainedMedium optimization improved chitinase production by 6-fold increase in activityAbstractChitin is a polysaccharide compound composed of N-acetylglucosamine (NAG), which is linked by β-1,4-glycoside bonds. In producing NAG from chitin, enzymatic method using chitinase offer advantages compared to chemical degradation. Streptomyces sp. PB2 is a good candidate of chitinase producer which was previously isolated from shrimp pond sediment. However, optimization of chitinase production by Streptomyces sp. PB2 is required for large-scale production of this enzyme. This study aimed to find the optimal medium composition to increase the chitinase enzyme activity of Streptomyces sp. PB2 using the Response Surface Method. Initial screening was done to determine additional carbon and nitrogen sources in colloidal chitin broth suitable for increasing chitinase activity. Optimization of the medium composition was conducted using the Plackett-Burman design to determine the critical components in the colloidal chitin broth medium and continued by Box-Behnken model to optimize the concentration of the medium components. Chitinase activity was obtained by measuring the amount of reducing sugar (NAG) released from enzymatic reaction using DMAB reagent by means of spectrophotometer. The medium components showing high contribution in increasing chitinase activity were K2HPO4, colloidal chitin and peptone, with the confidence level value of 0.66, 0.48, and 0.38, respectively. The Box-Behnken model analysis shows that the combination of K2HPO4 0.007 g/ml, colloidal chitin 1.5 g/ml and peptone 1.5 g/ml in colloidal chitin broth are the optimal medium for Streptomyces sp. PB2, resulted in chitinase activity of 0.0125 U/ml. The increase of 6-fold in chitinase activity was achieved in this study.