Maximum Theoretical Yield Research Articles

Optimized Acetic Acid Production by Mixed Culture of Saccharomyces cerevisiae TISTR 5279 and Gluconobacter oxydans TBRC 4013 for Mangosteen Vinegar Fermentation Using Taguchi Design and Its Physicochemical Properties.

This research investigates the enhancement of acetic acid production in the mangosteen vinegar fermentation process through mixed-culture fermentation involving S. cerevisiae TISTR 5279 and G. oxydans TBRC 4013, alongside an analysis of the resulting mangosteen vinegar's qualities and properties using Taguchi Experimental Design (TED). It focuses on key parameters, such as the juice concentration, inoculum ratio, and pasteurization conditions, to optimize acetic acid production. The findings highlight that the unpasteurized condition exerts the most significant influence on acetic acid production yield (p < 0.01), followed by the 3:1 inoculum ratio of S. cerevisiae TISTR 5279 to G. oxydans TBRC 4013 and a 10% mangosteen concentration. The achieved theoretical maximum yield of acetic acid on day 21 was 85.23 ± 0.30%, close to the predicted 85.33% (p > 0.05). Furthermore, the highest recorded acetic acid concentration reached 5.34 ± 0.92%. On day 14 of fermentation, the maximum productivity and yield were 3.81 ± 0.10 g/L/h and 0.54 ± 0.22 g/g, respectively. The resulting mangosteen vinegar exhibited elevated levels of total phenolic content (359.67 ± 47.26 mg GAE/100 mL), total flavonoid content (12.96 ± 0.65 mg CAE/100 mL), and anti-DPPH radical activity (17.67 ± 0.22%), suggesting potential health benefits. Beyond these chemical aspects, the mangosteen vinegar displayed distinct physical and chemical characteristics from the original mangosteen juice, possibly conferring additional health advantages. These findings are promising for industrial vinegar fermentation models and propose the potential use of the product as a valuable dietary supplement.

Continuous wheat-cotton residue incorporation combined with potassium fertilizer improved cotton root production capacity and constructed an optimized photosynthate distribution structure for high seedcotton yield

ABSTRACT In order to strengthen the cognition on synergy between crop residue incorporation and K, a continuous positioning experiment was carried out in 2020 and 2021. Four crop residue incorporation (CK, residue removal, WR, CR, and WR+CR, denoted wheat, cotton, and wheat and cotton residue incorporation) and three K rates (0, 150, and 225 kg K2O ha−1, denoted as K0, K150, and K225, respectively) were set. Compared with CK-K0, WR+CR-K150 increased seed cotton yield by 30.2% which reached the yield level of CK-K225. Taking the maximum theoretical seed cotton yield under CK as target yield, WR+CR, WR, and CR could achieve the same yield level with 59%–62%, 41%–49%, and 35%–43% less K fertilizer, respectively. Higher load capacity of root (LCR), boll loading of root (BLR) and lower root–shoot ratio (R/S) were observed at the boll-opening stage under the combined condition. When R/S, LCR and BLR were 0.12 g g−1, 4.00 g g−1 and 1.12 boll g−1, cotton could achieve maximum theoretical yield. 13C labeling result showed that WR+CR-K150 increased reproductive organ distribution proportion by 30.5% on average as compared with CK-K0. Thus, WR+CR-K150 can increase seed cotton yield by improving cotton root production capacity and increasing the photosynthate distribution proportion in reproductive organ.

A novel strategy for l-arginine production in engineered Escherichia coli

Backgroundl-arginine is an important amino acid with applications in diverse industrial and pharmaceutical fields. n-acetylglutamate, synthesized from l-glutamate and acetyl-CoA, is a precursor of the l-arginine biosynthetic branch in microorganisms. The enzyme that produces n-acetylglutamate, n-acetylglutamate synthase, is allosterically inhibited by l-arginine. l-glutamate, as a central metabolite, provides carbon backbone for diverse biological compounds besides l-arginine. When glucose is the sole carbon source, the theoretical maximum carbon yield towards l-arginine is 96.7%, but the experimental highest yield was 51%. The gap of l-arginine yield indicates the regulation complexity of carbon flux and energy during the l-arginine biosynthesis. Besides endogenous biosynthesis, n-acetylglutamate, the key precursor of l-arginine, can be obtained by chemical acylation of l-glutamate with a high yield of 98%. To achieve high-yield production of l-arginine, we demonstrated a novel approach by directly feeding precursor n-acetylglutamate to engineered Escherichia coli.ResultsWe reported a new approach for the high yield of l-arginine production in E. coli. Gene argA encoding n-acetylglutamate synthase was deleted to disable endogenous biosynthesis of n-acetylglutamate. The feasibility of external n-acetylglutamate towards l-arginine was verified via growth assay in argA− strain. To improve l-arginine production, astA encoding arginine n-succinyltransferase, speF encoding ornithine decarboxylase, speB encoding agmatinase, and argR encoding an arginine responsive repressor protein were disrupted. Based on overexpression of argDGI, argCBH operons, encoding enzymes of the l-arginine biosynthetic pathway, ~ 4 g/L l-arginine was produced in shake flask fermentation, resulting in a yield of 0.99 mol l-arginine/mol n-acetylglutamate. This strain was further engineered for the co-production of l-arginine and pyruvate by removing genes adhE, ldhA, poxB, pflB, and aceE, encoding enzymes involved in the conversion and degradation of pyruvate. The resulting strain was shown to produce 4 g/L l-arginine and 11.3 g/L pyruvate in shake flask fermentation.ConclusionsHere, we developed a novel approach to avoid the strict regulation of l-arginine on ArgA and overcome the metabolism complexity in the l-arginine biosynthesis pathway. We achieve a high yield of l-arginine production from n-acetylglutamate in E. coli. Co-production pyruvate and l-arginine was used as an example to increase the utilization of input carbon sources.

Citrate Synthase Overexpression of Pseudomonas putida Increases Succinate Production from Acetate in Microaerobic Cultivation.

Acetate is an end-product of anaerobic biodegradation and one of the major metabolites of microbial fermentation and lingo-cellulosic hydrolysate. Recently, acetate has been highlighted as a feedstock to produce value-added chemicals. This study examined acetate conversion to succinate by citrate synthase (gltA)-overexpressed Pseudomonas putida under microaerobic conditions. The acetate metabolism is initiated with the gltA enzyme, which converts acetyl-CoA to citrate. gltA-overexpressing P. putida (gltA-KT) showed an ∼50% improvement in succinate production compared to the wild type. Under the optimal pH of 7.5, the accumulation of succinate (4.73 ± 0.6 mM in 36 h) was ∼400% higher than that of the wild type. Overall, gltA overexpression alone resulted in 9.5% of the maximum theoretical yield in a minimal medium with acetate as the sole carbon source. This result shows that citrate synthase is important in acetate conversion to succinate by P. putida under microaerobic conditions.

Determination of Phosphorus Fertilizer Dose for Rice Using Mitscherlich-Bray Equation

Soil fertility maps in India showed that more than 90% of Indian soils are deficient in available phosphorus (P) although built-up is also reported in some areas. In this study, the modified Mitscherlich–Bray (MB) response equation was used to generate P fertilizer rates for aerobic rice by supplying with graded dose of P fertilizers. Three strip of different P gradient was created. Response of aerobic rice to added P suggested that crop showed a diminishing return with increasing dose of P. The data fitted to Mitscherlich-Bray (MB) equation showed that the theoretical maximum yield was estimated to be 60.847 (±0.394) q ha-1, the value of c related to the efficiency of the soil and fertilizer P is 0.084 (±0.008) and the R2 calculated using the uncorrected sums of squares is 0.988 that the MB equation is quite reliable. The estimated P rates for rice based on soil test values, price of fertilizers/price of crop ratio, and marginal rate of return would range from 57 – 68 kg ha-1 and this is much higher than the general recommended dose of 22 kg ha-1.

Hydrogen production from an on-board reformer for a natural gas engine: A thermodynamics study

In the present study, for an insight into the optimizing windows of comprehensive energy efficiency for open-loop system of marine NG engine and reformer, a peculiar thermodynamic equilibrium model for simulating the exhaust gas-fuel reforming process is established using equilibrium constant and experimental results. The accuracy of the model is evaluated by comparing numerical simulations with data derived from experiment of the open-loop operation system. Accordingly, the effect of engine loads and excess air (λ) as well as reformer feedstocks on maximum theoretical reforming characteristics are investigated. In addition, the energetic distribution in open-loop operation system can be clarified by the first law of thermodynamic. The results shown that fuel conversion toward H2 is highly selective due to the enhancement of reaction temperature with increasing engine loads. Especially, under 75% engine load, the maximum theoretical H2 yield reaches up to approximately 42.3% when λ = 1.4, CH4/O2 (M/O) = 1.5 and H2O/CH4 (S/M) = 2; The high λ will dilute the feed concentration of the reformer, thereby inhibiting the reforming reaction moving toward H2 production. Hence, an appropriate λ (1.4) can maximize the hydrogen production capacity of the reformer. In addition, according to the energy distribution of the open-loop system, the theoretical reforming energy efficiency of the reformer reaches a peak of 93.5% at S/M = 2 and M/O = 5. However, it can be found that M/O should be maintained above 1.5 to acquire optimal reforming energy utilization efficiency of system. Summarily, the optimal operation conditions for the reformer in open-loop operation system are confirmed: M/O = 1.5–2.5 and S/M = 1.5–2 under 75% engine load, which could fulfill efficient reforming performance.

Grape Stalk Valorization: An Efficient Re-Use of Lignocellulosic Biomass through Hydrolysis and Fermentation to Produce Lactic Acid from Lactobacillus rhamnosus IMC501

Lactobacillus rhamnosus is a homofermentative probiotic strain that was previously demonstrated to grow on lignocellulosic-derived raw materials and to convert glucose into L-lactic acid (LA) with yields that vary between 0.38 and 0.97 g/g. Lactic acid is a key platform chemical, largely applied in different biotechnological fields (spanning from the pharmaceutical to the food sector) and also as a building block for the production of biodegradable polymers. In the present study, grape stalks were evaluated as sources of fermentable sugars for the growth of L. rhamnosus IMC501 and for the production of LA, since millions of hectoliters of wine are produced every year worldwide, generating a huge amount of waste. Although grape stalks are quite recalcitrant, the combination of a steam explosion pre-treatment with optimized two-step hydrolysis and commercial enzymes (Cellic-CTec2) allowed us to obtain a cellulose conversion efficiency of about 37% and to develop small-scale 2 L batch fermentation processes. Results successfully demonstrate that L. rhamnosus IMC501 can tolerate biomass-derived inhibitors and grow on grape stalk hydrolysate without the need for additional sources of nitrogen or other nutritional elements, and that the strain can convert all glucose present in the medium into LA, reaching the maximal theoretical yield.

Modular engineering of Escherichia coli for high-level production of l-tryptophan

As an essential amino acid, l-tryptophan is widely used in food, feed and medicine sectors. Nowadays, microbial l-tryptophan production suffers from low productivity and yield. Here we construct a chassis E. coli TRP3 producing 11.80 g/L l-tryptophan, which was generated by knocking out the l-tryptophan operon repressor protein (trpR) and the l-tryptophan attenuator (trpL), and introducing the feedback-resistant mutant aroGfbr. On this basis, the l-tryptophan biosynthesis pathway was divided into three modules, including the central metabolic pathway module, the shikimic acid pathway to chorismate module and the chorismate to tryptophan module. Then we used promoter engineering approach to balance the three modules and obtained an engineered E. coli TRP9. After fed-batch cultures in a 5 L fermentor, tryptophan titer reached to 36.08 g/L, with a yield of 18.55%, which reached 81.7% of the maximum theoretical yield. The tryptophan producing strain with high yield laid a good foundation for large-scale production of tryptophan.

Valorization of beetle infected spruce to produce textile fibers and biofuels: Environmental sustainability evaluated by life cycle assessment

To achieve a viable forest-based biorefinery, both the carbohydrate and lignin parts of the raw material should be valorized. While lignin-first approaches have successfully been applied to hardwoods, where up to 50% of the lignin –close to the ‘theoretical maximum yield’– has been transformed to valuable monophenols; limited studies have targeted softwoods. Softwood lignin comprises lower amount of beta-ether bonds and this results in lower theoretical and observed yields of monophenols in reductive catalytic fractionation (RCF): below 5 wt% yield of initial biomass has been reported. In this study, we use beetle infected spruce, a softwood, as raw material. A fast fractionation was developed to give a pulp and a lignin fraction in the absence of transition metal catalysts. The carbohydrate matrix was valorized to dissolving grade pulp in 37 wt% from biomass (86% yield), and successfully spun to Lyocell fibers. The lignin fraction was dissolved in furfural –operating as green ‘solubility-enhancing-agent’– to blend lignin in inert carrier liquids to promote controlled hydrotreatment to yield biofuels in 10 wt% (60% carbon yield) from initial biomass. Life cycle assessment (LCA) of the value-chain showed improved sustainability in several footprint categories compared to cotton production. Thus, upgrading of a considered forestry waste to high value textile fibers and biofuels has been achieved: in case of lignin beyond the ‘theoretical maximum yield’. This is an important step to mitigate a future growing demand of textiles without negatively affecting irrigation or land use.

Optimization of macronutrients application in Terminalia tomentosa (Asan) for sustainable tasar silk production

Aim: The aim of the present study was to optimise the nutrient requirements for Terminalia tomentosa (Asan) plant to increase the quality and quantity of leaves. Methodology: This study used the Mitscherlich-Bray equation to formulate NPK requirements for the Asan plant. Independent experimental setups of N (5 levels), P (5 levels), and K (5 levels) designed in RCBD with three replications were carried out concurrently. Calculations were made to determine the theoretical maximum yield, the NPK constants c and c1, the NPK fertiliser recommendations for the Asan plant at various soil fertility levels, and the ideal fertiliser rates. Results: Fertiliser recommendations were developed for a typical range of soil test values, but they still required additional field verification tests. The theoretical maximum yields determined by the Mitscherlich-Bray equation were 599.79g, 587.49 g, and 562.34 g per 50 leaves of the Asan plant for NPK, respectively. The study demonstrated that it is critical to consider the inherent soil fertility when developing fertiliser recommendations for Asan that will increase both leaf yield and overall productivity. It showed that soil K was less efficiently utilised by the Asan plant compared to the other soil nutrients. The c1/c ratio of the P experiment was lowest compared to the c1/c ratio values of N and K experiments, indicating that the Asan plant was more responsive to P fertilisation than other macronutrient fertilisation Interpretation: The fertiliser recommendation chart serves the farmers to manage the Asan plants and is more beneficial for harvesting quality cocoons without degrading the ecosystem. Key words: Asan, Baripada, Macronutrients, Odisha, Tasar silk

Screening of New Industrially Important Bacterial Strains for 1,3-Propanediol, 2,3-Butanediol and Ethanol Production through Biodiesel-Derived Glycerol Fermentations.

A study on the ability of new microbial strains to assimilate biodiesel-derived glycerol at low purity (75% w/w) and produce extra-cellular platform chemical compounds of major interest was carried out. After screening several bacterial strains under different fermentation conditions (e.g., pH, O2 availability, glycerol purity), three of the screened strains stood out for their high potential to produce valued-added products such as 2,3-butanediol (BDO), 1,3-propanediol (PDO) and ethanol (EtOH). The results indicate that under aerobic conditions, Klebsiella oxytoca ACA-DC 1581 produced BDO in high yield (YBDO/Gly = 0.46 g/g, corresponding to 94% of the maximum theoretical yield; Ymt) and titer, while under anaerobic conditions, Citrobacter freundii NRRL-B 2645 and Enterobacter ludwigii FMCC-204 produced PDO (YPDO/Gly = 0.56 g/g, 93% of Ymt) and EtOH (YEtOH/Gly = 0.44 g/g, 88% of Ymt), respectively. In the case of C. freundii, the regulation of pH proved to be mandatory, due to lactic acid production and a subsequent drop of pH that resulted in fermentation ceasing. In the fed-batch culture of K. oxytoca, the BDO maximum titer reached almost 70 g/L, the YBDO/Gly and the mean productivity value (PrBDO) were 0.47 g/g and 0.4 g/L/h, respectively, while no optimization was imposed. The final BDO production obtained by this wild strain (K. oxytoca) is among the highest in the international literature, although the bioprocess requires optimization in terms of productivity and total cost. In addition, for the first time in the literature, a strain from the species Hafnia alvei (viz., Hafnia alvei ACA-DC 1196) was reported as a potential BDO producer. The strains as well as the methodology proposed in this study can contribute to the development of a biorefinery that complements the manufacture of biofuels with high-value biobased chemicals.

Extracellular production of a thermostable Cellvibrio endolytic β-agarase in Escherichia coli for agarose liquefaction

Four GH16 family β-agarases (GH16A, GH16B, GH16C, and GH16D), originated from an agarolytic bacterium Cellvibrio sp. KY-GH-1, were expressed in an Escherichia coli system and their activities were compared. Only GH16B (597 amino acids, 63.8 kDa), with N-terminal 22-amino acid signal sequence, was secreted into the culture supernatant and demonstrated a robust endolytic agarose hydrolyzing activity for producing neoagarotetraose (NA4) and neoagarohexaose (NA6) as end products. The optimal temperature and pH for the enzyme activity were 50 °C and 7.0, respectively. The enzyme was stable up to 50 °C and over a pH range of 5.0–8.0. The kinetic parameters, including Km, Vmax, kcat, and kcat/Km, of GH16B β-agarases for agarose were 14.40 mg/mL, 542.0 U/mg, 576.3 s−1, and 4.80 × 106 s−1 M−1, respectively. The addition of 1 mM MnCl2 and 15 mM tris(2-carboxyethyl)phosphine enhanced the enzymatic activity. When agarose or neoagaro-oligosaccharides were used as substrates, the end products of enzymatic catalysis were NA4 and NA6, whereas agaropentaose was produced along with NA4 and NA6 when agaro-oligosaccharides were used as substrates. Treatment of 9%[w/v] melted agarose with the enzyme (1.6 µg/mL) under continuous magnetic stirring at 50 °C for 14 h resulted in efficient agarose liquefaction into NA4 and NA6. Purification of NA4 and NA6 from the enzymatic hydrolysate (9%[w/v] agarose, 20 mL) via Sephadex G-15 column chromatography yielded ~ 650 mg NA4/~ 900 mg NA6 (i.e., ~ 85.3% of the theoretical maximum yield). These findings suggest that the recombinant thermostable GH16B β-agarase is useful for agarose liquefaction to produce NA4 and NA6.Graphical

An eco-friendly approach of biodiesel production from tannery fleshing wastes by crude neutral protease enzyme

A new approach for extracting fat from tannery fleshing wastes (TFW) was established by hydrolyzing in water using a crude neutral protease enzyme. The bacterial strain for protease preparation was isolated from the waste dumping site of Institute of Leather Engineering and Technology of the University of Dhaka. The crude enzyme thus obtained was found highly active at 55 °C and pH 8.0, with a substrate concentration of 2%. Several reaction parameters, such as enzyme concentration, hydrolysis temperature and duration, were optimized using response surface methodology (RSM). The detailed analysis data by RSM showed 31.33% enzyme to dry weight of fleshing, 2.874 h of hydrolysis, and at 65.23 °C temperature to be the optimum for maximum theoretical fat yield of 38.46%. The laboratory experiments under optimum conditions resulted 34.9% fat yield with an error of 10.17%. The fleshing fat was transesterified in methanol into biodiesel using a recyclable magnetic nano catalyst with a 98% conversion and glycerol as a byproduct. The FT-IR spectroscopic results demonstrated an absorption of CO stretching at 1740 cm−1 for α, β-unsaturated esters in the biodiesel and its fatty acid ethyl ester. The 1H-NMR spectroscopy revealed a singlet peak of methoxy protons at 3.65 ppm and a triplet at 2.26–2.30 ppm for α-CH2 protons that confirmed the presence of unsaturated fatty acids with a carbonyl hydrogen double bond peak at 2.00–2.01 ppm. The GC-MS data of the biodiesel comprises of ethyl E−11-hexa-decanoate, ethyl myristate, palmitate, stearate, and decanoate. The results of various fuel parameters of the biodiesel were measured and compared with standard biodiesel EN14214 which revealed that it has comparable fuel properties to the standard. The higher calorific value (38.5 MJ kg−1) and flash point (152 °C) of the biodiesel than the standard, indicating its high potential and ease of storage stability than standard biodiesel.

Fungal-Lactobacteria Consortia and Enzymatic Catalysis for Polylactic Acid Production.

Polylactic acid (PLA) is the main biobased plastic manufactured on an industrial scale. This polymer is synthetized by chemical methods, and there is a strong demand for the implementation of clean technologies. This work focuses on the microbial fermentation of agro-industrial waste rich in starch for the production of lactic acid (LA) in a consolidated bioprocess, followed by the enzymatic synthesis of PLA. Lactic acid bacteria (LAB) and the fungus Rhizopus oryzae were evaluated as natural LA producers in pure cultures or in fungal-lactobacteria co-cultures formed by an LAB and a fungus selected for its metabolic capacity to degrade starch and to form consortia with LAB. Microbial interaction was analyzed by scanning electron microscopy and biofilm production was quantified. The results show that the fungus Talaromyces amestolkiae and Lactiplantibacillus plantarum M9MG6-B2 establish a cooperative relationship to exploit the sugars from polysaccharides provided as carbon sources. Addition of the quorum sensing molecule dodecanol induced LA metabolism of the consortium and resulted in improved cooperation, producing 99% of the maximum theoretical yield of LA production from glucose and 65% from starch. Finally, l-PLA oligomers (up to 19-LA units) and polymers (greater than 5 kDa) were synthetized by LA polycondensation and enzymatic ring-opening polymerization catalyzed by the non-commercial lipase OPEr, naturally produced by the fungus Ophiostoma piceae.

Ethanol production from non-detoxified hardwood spent sulfite liquor in submerged fed-batch culture using advanced yeasts

To improve process feasibility, it is essential to use hardwood spent sulfite liquor (HSSL) as the main feedstock for bioethanol production, without prior detoxification. In addition, operating at large-scale under cost-effective conditions such as a small inoculum size (< 1 g/L), pH 5, using industrially acceptable nutrients, and without sugar addition, will require the use of harsh, concentrated HSSL streams. The potential of non-detoxified HSSL as a feedstock for ethanol production using two recombinant Saccharomyces cerevisiae strains, CelluX™4 and TFA7, was assessed. The inhibitory effect of non-detoxified HSSL was mitigated, and the ethanol titer increased from 4.1 to 7.9 g/L when pulse fed-batch was used instead of batch production, with CelluX™4 performing best. Both strains made use of the xylose isomerase (XI) pathway, with strain TFA7 engineered for increased tolerance against inhibitors. By administering concentrated HSSL in pulses to shake-flask cultures, the ethanol titer could be increased by approximately 50–90% when compared to simple batch cultures supplemented with 20%, 40%, and 60% (v/v) dilutions of HSSL. CelluX™4 was used in non-aerated, non-sterile 5-L bioreactor fermentations with a low cell concentration (< 1 g/L), pH 5, and 5 g/L corn steep liquor (CSL) as the nitrogen source. In comparison, undiluted HSSL was fed continuously to obtain a final 65% (v/v) HSSL supplementation, which corresponded to a total sugar concentration of 70.8–80.8 g/L. Despite the use of harsher, concentrated feedstock and inexpensive process conditions, the reactor fed-batch fermentations obtained ethanol yields of 0.35–0.43 g/g, which, based on a maximum theoretical ethanol yield of 0.51 g/g of hexoses or pentoses, corresponds to yield efficiencies of 68.6 and 84.3%. This illustrates an improvement on the highest titers reported in the literature for non-detoxified HSSL. The use of the advanced industrial S. cerevisiae strain, CelluX™4, combined with a fed-batch strategy, offers an inexpensive and straightforward process with real upscaling potential for industrial HSSL fermentations.

N-Nitrosamine Formation in Pharmaceutical Solid Drug Products: Experimental Observations

The potential presence of N-nitrosamines in medicinal products has become a matter of concern for health authorities and pharmaceutical companies. However, very little information is available in published literature on N-nitrosamine formation within pharmaceutical drug products. In response, experiments were undertaken to test if secondary and tertiary amines present in solid drug products could undergo nitrosation due to the presence of nitrite in the excipients used in the manufacture of the drug product. This work focused on solid dosage forms exploring several model amines of varying chemical structure, solubility and pKa which were formulated using common excipients with and without added nitrite. Monitoring the formation of the N-nitrosamines after processing and upon stressed stability conditions showed that N-nitrosamine formation can occur in solid drug product formulations. The results show that the rate and extent of N-nitrosamine formation depend upon the solubility of the amine, level of nitrite, expected local acidity in water layers within the drug product and mode of processing. Our findings agree with the rank order of dosage form risk from the published EFPIA workflows for quality risk management of N-nitrosamine risks in medicines (EFPIA, 2022): amorphous > wet granulation > direct compression > dry blends. In all cases the level of N-nitrosamine formation in solid dosage forms plateaued at a level that was significantly lower than the maximum theoretical yield based on the level of nitrite present. Trace secondary amine impurities were shown to be a significantly lower risk relative to cases containing a secondary amine present at drug substance levels. A comparison of secondary and simple tertiary alkylamine reactivity showed the tertiary amine to be significantly less reactive with nitrite.

Functional evaluation of non-oxidative glycolysis in Escherichia coli in the stationary phase under microaerobic conditions

In microbial bioproduction, CO2 emissions via pyruvate dehydrogenase in the Embden-Meyerhof pathway, which converts glucose to acetyl-CoA, is one of the challenges for enhancing carbon yield. The synthetic non-oxidative glycolysis (NOG) pathway transforms glucose into three acetyl-CoA molecules without CO2 emission, making it an attractive module for metabolic engineering. Because the NOG pathway generates no ATP and NADH, it is expected to use a resting cell reaction. Therefore, it is important to characterize the feasibility of the NOG pathway during stationary phase. Here, we experimentally evaluated the invivo metabolic flow of the NOG pathway in Escherichia coli. An engineered strain was constructed by introducing phosphoketolase from Bifidobacterium adolescentis into E.coli and by deleting competitive reactions. When the strain was cultured in magnesium-starved medium under microaerobic conditions, the carbon yield of acetate, an end-product of the NOG pathway, was six times higher than that of the control strain harboring an empty vector. Based on the mass balance constraints, the NOG flux was estimated to be between 2.89 and 4.64mmolg-1h-1, suggesting that the engineered cells can convert glucose through the NOG pathway with enough activity for bioconversion. Furthermore, to expand the application potential of NOG pathway-implemented strains, the theoretical maximum yields of various useful compounds were calculated using flux balance analysis. This suggests that the theoretical maximum yields of not only acetate but also lactam compounds can be increased by introducing the NOG pathway. This information will help in future applications of the NOG pathway.

A Simulation Study on Optimization of Sowing Time of Maize (Zea mays L.) for Maximization of Growth and Yield in the Present Context of Climate Change under the North China Plain

Adjusting the sowing dates of crops is an effective measure for adapting them to climate change, but very few studies have explained how the optimum sowing dates can be determined. In this study, we used the sowing date field data from 2018 to 2021 from Hebei Gucheng Agricultural Meteorology National Observation and Research Station to analyze the effects of the sowing date on growth, development, and yield of maize, and to quantify the impact of light-temperature potential productivity on different stages of the yield formation. The results showed that delayed sowing decreased the vegetative growth period (VGP) and increased the reproductive growth period (RGP) of maize. The light-temperature potential productivity of the whole growth (WG) period had an exponential relationship with the theoretical yield. At least 14,614.95 kg ha−1 of light-temperature potential productivity was needed to produce grain yield. The maximum theoretical yield was approximately 18,052.56 kg ha−1, as indicated by the curve simulation results. The influence of light-temperature potential productivity on theoretical yield was as follows: VGP &gt; RGP &gt; vegetative and reproductive period (VRP). Accordingly, a method for determining the sowing time window based on VGP was established, and the optimal sowing dates were estimated for 1995–2021 and the SSP2-4.5 scenario in CMIP6 in the middle of this century (2030–2060). The simulation results showed that the optimum sowing date of maize “Lianyu 1” at the study site was 20–25 May in 1995–2021. In the middle of this century, the optimal sowing time of maize was ahead of schedule and the suitable sowing window was increased slightly. We conclude that advancing the sowing date of maize is a practical strategy for enhancing yield in the context of climate warming, and this strategy will provide a meaningful reference for scientific optimization of sowing dates to adapt maize to climate change.

A novel simulation calculation model based on photosynthetic electron transfer for microalgal growth prediction in any photobioreactor

The microalgal research field is currently lacking a unified theoretical computing system to explain various experimental results related to microalgal growth. Thus a novel universal theoretical model was created to predict microalgal growth with carbon dioxide (CO2) fixation in any cultivation system. First, a new “light-effect colorimetric method” was proposed to estimate the actual f2 value of suspended microalgal cells during regular experimentation using a formula explaining the photosynthetic effective electron transfer rate (ETR = PFD·ΦII·f1·f2), which only requires the use of a simple spectrophotometer. A mathematical relationship between photosynthetic electron transfer and the microalgal growth rate was then identified based on this modified ETR by simplifying factors influencing the cultivation conditions (e.g., nutrients and CO2) into the slope and intercept of this formula. Subsequently, software was written to allow the above relationship to stimulate any 3-D microalgal cultivation system. Many example cases were conducted to clarify the significance and application of this theoretical model. It was found that the average ETR of a cultivation system describes microalgal tolerance to high CO2 concentrations. A photobioreactor at any given location under a certain light condition has a theoretical maximum yield of microalgal biomass, irrespective of how the other cultivation conditions change. A new concept of “biological similarity” is proposed as a basic principle for scaling up microalgal experiments with photosynthetic CO2 fixation to perform a repeated growth curve with < 5 % error. Finally, a “multi-batch dilution method” was demonstrated to increase the microalgal biomass yield by 64.4 % over a short cultivation period. General application of this calculation model would change the empirical status of microalgal engineering designs.

Role of reaction adsorption on the production of 5-hydroxymethylfurfural from fructose under microwave hydrothermal process

5-Hydroxymethylfurfural (HMF) has been considered a valuable biomass-derived platform chemical that can be produced by hexose dehydration in the presence of an acid. However, the yield of HMF is always reduced because of side reactions such as rehydration and condensation. In this work, the reactive adsorption process of fructose dehydration to HMF catalyzed by hydrochloric acid under microwave condition was studied. BP2000 has better adsorption capacity than activated carbon (AC) in reactive adsorption, and addition of BP2000 increases the HMF yield. The maximum theoretical yield of HMF was 65 % obtained by adding 39 g L−1 BP2000 and reacting for 4 min at 160 °C under a microwave hydrothermal condition. It was discovered thatmicrowave hydrothermal technology (MHT) could significantly increase efficiency and reduce reaction time. Reactive adsorption could efficiently buffer HMF from side reactions when reaction conditions became severe, thereby increasing the HMF yield. Reactive adsorption provides a more sustainable method for HMF production and separation.