Determining the Optimal Biomass of Macrophytes during the Ecological Restoration Process of Eutrophic Shallow Lakes

Many studies have shown that macrophytes play a significant role in controlling eutrophication; however, only a few of these are based on macrophyte biomass. Based on the growth characteristic of macrophytes, we propose an approach for the assessment of the optimal biomass of macrophytes in the decay and growth periods in Lake Datong (a shallow lake), using a lake ecological model. The results showed that the pollution load of the lake should be reduced by 50% while conforming to the Environmental Quality Standards for Surface Water (EQSSW) Class Ⅲ. In contrast, with an increase in the pollution load of 5%, the results indicate that the lake may deteriorate to a turbid state over the next few years. The macrophyte biomass should be harvested during the decay period, when 80% biomass is beneficial to the water quality of the eutrophic shallow lake. Based on macrophyte simulation from 2020–2024, the wet biomass of macrophytes should be controlled at 5.5 kg/m2. The current macrophyte biomass in Lake Datong is four-fold higher than the simulated optimal biomass. This study provides a reference for the adequate ecological restoration of the lake and its subsequent maintenance, as well as scientific support for improving the comprehensive evaluation standard of healthy lakes and the theoretical basis of lake ecological restoration.

Antifungal activity of extracts of Melia azedarach and Ageratum conyzoides against Lasiodiplodia pseudotheobromae through in vitro test

Lasiodiplodia pseudotheobromae is one of the pathogens of the cocoa dieback disease. Currently, the disease is considered a significant disease in cocoa, which is a newly emerging disease in Sulawesi. The control tools and methods remain unexplored comprehensively. The main objective of this study was to evaluate Melia azedarach and Ageratum conyzoides leaf extract to inhibit the growth of the L. pseudotheobromae. Three different concentrations were applied for each weed extract, namely: 1%, 3%, and 5%. The experiment was conducted through the poison food technique method both in solid medium and liquid medium. M. azedarach and A. conyzoides were significantly inhibited the colony growth of L. pseudotheobromae in all concentrations in solid medium. However, A. conyzoides 5% performed well to suppress the colony growth of L. pseudotheobromae (42.7%), followed by M. azedarach 5% (16.0%). The mycelium biomass of L. pseudotheobromae was significantly inhibited by M. azedarach and A. conyzoides as well. A. conyzoides 5% showed a higher inhibition of the fungal biomass either wet biomass (90.3%) or dry biomass (95.5%), followed by M. azedarach 5% both wet biomass (85.6%) and dry biomass (78.1%). M. azedarach and A. conyzoides remain to inhibit the colony growth and fungal biomass regardless of the type of concentrations. M. azedarach and A. conyzoides can potentially be an option for controlling dieback disease caused by L. pseudotheobromae.

Biocrude Production from Hydrothermal Liquefaction of Chlorella: Thermodynamic Modelling and Reactor Design

Hydrothermal liquefaction can directly and efficiently convert wet biomass into biocrude with a high heating value. We developed a continuous hydrothermal liquefaction model via Aspen Plus to explore the effects of moisture content of Chlorella, reaction pressure and temperature on thermodynamic equilibrium yields, and energy recoveries of biocrude. We also compared the simulated biocrude yield and energy recoveries with experiment values in literature. Furthermore, vertical and horizontal transportation characteristics of insoluble solids in Chlorella were analyzed to determine the critical diameters that could avoid the plugging of the reactor at different flow rates. The results showed that the optimum moisture content, reaction pressure, and reaction temperature were 70–90 wt%, 20 MPa, and 250–350 °C, respectively. At a thermodynamic equilibrium state, the yield and the energy recovery of biocrude could be higher than 56 wt% and 96%, respectively. When the capacity of the hydrothermal liquefaction system changed from 100 to 1000 kg·h−1, the critical diameter of the reactor increased from 9 to 25 mm.

Expression and Refolding of the Plant Chitinase From Drosera capensis for Applications as a Sustainable and Integrated Pest Management

Recently, the study of chitinases has become an important target of numerous research projects due to their potential for applications, such as biocontrol pest agents. Plant chitinases from carnivorous plants of the genus Drosera are most aggressive against a wide range of phytopathogens. However, low solubility or insolubility of the target protein hampered application of chitinases as biofungicides. To obtain plant chitinase from carnivorous plants of the genus Drosera in soluble form in E.coli expression strains, three different approaches including dialysis, rapid dilution, and refolding on Ni-NTA agarose to renaturation were tested. The developed « Rapid dilution » protocol with renaturation buffer supplemented by 10% glycerol and 2M arginine in combination with the redox pair of reduced/oxidized glutathione, increased the yield of active soluble protein to 9.5 mg per 1 g of wet biomass. A structure-based removal of free cysteines in the core domain based on homology modeling of the structure was carried out in order to improve the soluble of chitinase. One improved chitinase variant (C191A/C231S/C286T) was identified which shows improved expression and solubility in E. coli expression systems compared to wild type. Computational analyzes of the wild-type and the improved variant revealed overall higher fluctuations of the structure while maintaining a global protein stability. It was shown that free cysteines on the surface of the protein globule which are not involved in the formation of inner disulfide bonds contribute to the insolubility of chitinase from Drosera capensis. The functional characteristics showed that chitinase exhibits high activity against colloidal chitin (360 units/g) and high fungicidal properties of recombinant chitinases against Parastagonospora nodorum. Latter highlights the application of chitinase from D. capensis as a promising enzyme for the control of fungal pathogens in agriculture.

Optimisation of Culture media through Response surface methodology to improve Antioxidant activity of E. coli

Antioxidants play a significant role in oxidative stress management and health protection. One variable at a time response surface methodology (RSM) was used to formulate different composition of media to increase the antioxidant property of selected microorganism (Escherichia coli MTCC no. 40). 1, 1-diphenyl-2-picrylhydrazyl (DPPH) assays was used to measure antioxidant activity of selected microorganism. The reduction potentiality of DPPH radical was determined by the DPPH% antioxidant or scavenging activity of the solution. In the present study, we have measured antioxidant activity of both intracellular and extracellular metabolites in dry and wet extracellular metabolites in supernatant respectively. In DPPH assay, extracellular metabolites showed better antioxidant potential in comparison with the reference compound. The comparison was based on antioxidant activity in different responses (number 1-16) for both dry and wet biomass. According to the results maximum DPPH % antioxidant or scavenging activity was showed by response 9 (wet biomass) and response 6 (dry biomass) that is 24.8447 and 35.0142 respectively in comparison to standard (4.4636). Hence, response surface methodology is used in bioprocess technology to optimize the medium components which is the primary step involved to enhance the antioxidant activity of particular microorganism.

Comparative analysis of L-carnitine production by Yarrowia lipolytica in different culture conditions in biofuel waste and fatty acid-poor medium for commercial purposes

Background Yarrowia lipolytica is an oleaginous yeast with the ability to grow in a variety of hydrophilic and hydrophobic substrates, including industrial wastes, in which it produces and accumulates various nutrients. Methods The aim of the present study was to examine the presence of free L-carnitine in the biomasses of two Yarrowia lipolytica strains (A-101 and ATCC 9793) growing in biofuel waste and YPD medium. The cultivations of Y. lipolytica were performed in aerobic conditions at different temperatures (20–30°C) and pH values (4.0–7.0) of the media with and without the addition of precursors for L-carnitine production (trimethyllysine, iron, and L-ascorbic acid) in a laboratory scale or other substances (chromium, selenite, or zinc) in a pilot plant scale. Results Both tested Y. lipolytica strains grown in fatty acid-poor YPD medium contained endogenous free L-carnitine in their biomass with a maximum of 22.85 mg/100 g of wet biomass. The addition of L-carnitine precursors to the YPD medium exerted a significant effect on L-carnitine concentration in the yeast biomass, increasing it up to 250%. In turn, the biomass of both tested Y. lipolytica strains cultivated in the biofuel waste, irrespective of the culture conditions, contained below 1 mg of L-carnitine/100 g of wet biomass. However, the supplementation of the culture media with the L-carnitine precursors significantly increased the yield of the yeast biomass by 20–30% in the non-fermentable biofuel waste cultures. Moreover, the addition of chromium (III) chloride into the biofuel waste caused an increase in the free L-carnitine concentration in the yeast biomass up to 2.24 mg/100 g of dry weight. Conclusion Biomass of Y. lipolytica grown in the fat-poor medium contained free L-carnitine, in contrast to the biomass grown in the fat-rich biofuel waste. The very low amounts of L-carnitine in the biomass of Y. lipolytica grown in the crude biofuel waste suggest that the yeast is able to utilize almost the entire pool of free L-carnitine for growth and nutritional biomass production. However, the addition of chromium to the biofuel waste contributed to an increase in L-carnitine concentration in Y. lipolytica biomass.