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5-Aminolevulinic acid (5-ALA) is a non-proteinogenic amino acid essential for synthesizing tetrapyrrole compounds, including heme, chlorophyll, cytochrome, and vitamin B12. As a plant growth regulator, 5-ALA is extensively used in agriculture to enhance crop yield and quality. The complexity and low yield of chemical synthesis methods have led to significant interest in the microbial synthesis of 5-ALA. Advanced strategies, including the: enhancement of precursor and cofactor supply, compartmentalization of key enzymes, product transporters engineering, by-product formation reduction, and biosensor-based dynamic regulation, have been implemented in bacteria for 5-ALA production, significantly advancing its industrialization. This article offers a comprehensive review of recent developments in 5-ALA production using engineered bacteria and presents new insights to propel the field forward.

Genome engineering is extensively utilized in diverse scientific disciplines, advancing human welfare and addressing various challenges. Numerous genome engineering tools have been developed to modify genomic sequences. Among these, the CRISPR-Cas system has transformed the field and remains the most commonly employed genome-editing tool. However, the CRISPR-Cas system relies on induced double-strand breaks, with editing efficiency often limited by factors such as cell type and homologous recombination, impeding further progress. CRISPR-associated transposons (CASTs) represent programmable mobile genetic elements. CASTs identified as active were developed as CAST systems, which can perform RNA-guided DNA integration and are featured by high precision, programmability, and kilobase-level payload capacity. Moreover, CAST system allows for precise genome modifications independent of host DNA repair mechanisms, addressing the constraints of conventional CRISPR-Cas systems. It expands the genome engineering toolkit and is poised to become a representative of next-generation genome editing tools. This review thoroughly examines the research progress on CASTs, highlighting the current challenges faced in genome engineering based on CASTs, and offering insights into the ongoing development of this transformative technology., Competing Interests: Declaration of competing interest The authors declare that they have no financial or personal relationships that could have influenced the work presented in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

The development of high-performance strains and the continuous breakthrough of strain screening technology also pose challenges to downstream fermentation optimization and scale-up. Therefore, neural network models are utilized to optimize the fermentation process to meet the goals of boosting yield or lowering cost, with the use of artificial intelligence technology in conjunction with the peculiarities of the fermentation process. High-performance strains' yield rise and fermentation process amplification will be sped up with the aid of neural network models. This paper offers a helpful review for anyone interested in state-of-the-art microbial fermentation processes, as it thoroughly reviews the application of neural network models in predicting fermentation yield, optimizing the fermentation process, and monitoring the fermentation process., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Abscisic acid (ABA) is an important plant growth regulator with broad applications in agriculture, forestry, and other fields. Currently, the industrial production of ABA primarily relies on microbial fermentation using Botrytis cinerea , but its genetic toolbox is limited. To address this, we first screened 10 strong constitutive promoters from the genome of B. cinerea through transcriptomic analysis. The expression levels of the promoters covered a range of 3-4 orders of magnitude according to the measured β-glucuronidase activity. Subsequently, four promoters of different strength were used to balance the cofactor supply in B. cinerea . Overexpression of NADH kinase using the medium-strength promoter Pef1a significantly enhanced ABA production, resulting in a 32.26 % increase compared to the control. Finally, by combining promoter engineering with a push-pull strategy, we optimized the biosynthesis of ABA. The recombinant strain Pthi4:hmgr-Pef1a:a4, overexpressing HMGR under the Pthi4 promoter and Bcaba4 under the Pef1a promoter, achieved an ABA titer of 1.18 g/L, a 58.92 % increase. To our best knowledge, this is the first constitutive promoter library suitable for B. cinerea , providing important tools for the industrial production of ABA., Competing Interests: The authors declare that they have no competing financial interests., (© 2024 The Authors.)

Biomanufacturing, driven by technologies such as synthetic biology, offers significant potential to advance the bioeconomy and promote sustainable development. It is anticipated to transform traditional manufacturing and become a key industry in future strategies. Cell factories are the core of biomanufacturing. The advancement of synthetic biology and growing market demand have led to the production of a greater variety of natural products and increasingly complex metabolic pathways. However, this progress also presents challenges, notably the conflict between natural product production and chassis cell growth. This conflict results in low productivity and yield, adverse side effects, metabolic imbalances, and growth retardation. Enzyme co-localization strategies have emerged as a promising solution. This article reviews recent progress and applications of these strategies in constructing cell factories for efficient natural product production. It comprehensively describes the applications of enzyme-based compartmentalization, metabolic pathway-based compartmentalization, and synthetic organelle-based compartmentalization in improving product titers. The article also explores future research directions and the prospects of combining multiple strategies with advanced technologies., Competing Interests: Declaration of competing interest The authors declare that they have no competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Flavonoids, a significant group of natural polyphenolic compounds, possess a broad spectrum of pharmacological effects. Recent advances in the systematic metabolic engineering of yeast cell factories (YCFs) provide new opportunities for enhanced flavonoid production. Herein, we outline the latest research progress on typical flavonoid products in YCFs. Advanced engineering strategies involved in flavonoid biosynthesis are discussed in detail, including enhancing precursor supply, cofactor engineering, optimizing core pathways, eliminating competitive pathways, relieving transport limitations, and dynamic regulation. Additionally, we highlight the existing problems in the biosynthesis of flavonoid glucosides in yeast, such as endogenous degradation of flavonoid glycosides, substrate promiscuity of UDP-glycosyltransferases, and an insufficient supply of UDP-sugars, with summaries on the corresponding solutions. Discussions also cover other typical postmodifications like prenylation and methylation, and the recent biosynthesis of complex flavonoid compounds in yeast. Finally, a series of advanced technologies are envisioned, i.e., semirational enzyme engineering, ML/DL algorithn, and systems biology, with the aspiration of achieving large-scale industrial production of flavonoid compounds in the future.

Monoterpenoids are an important subclass of terpenoids that play important roles in the energy, cosmetics, pharmaceuticals, and fragrances fields. With the development of biotechnology, microbial synthesis of monoterpenoids has received great attention. Yeasts such Saccharomyces cerevisiae and Yarrowia lipolytica are emerging as potential hosts for monoterpenoids production because of unique advantages including rapid growth cycles, mature gene editing tools, and clear genetic background. Recently, advancements in metabolic engineering and fermentation engineering have significantly enhanced the accumulation of monoterpenoids in cell factories. First, this review introduces the biosynthetic pathway of monoterpenoids and comprehensively summarizes the latest production strategies, which encompass enhancing precursor flux, modulating the expression of rate-limited enzymes, suppressing competitive pathway flux, mitigating cytotoxicity, optimizing substrate utilization, and refining the fermentation process. Subsequently, this review introduces four representative monoterpenoids. Finally, we outline the future prospects for efficient construction cell factories tailored for the production of monoterpenoids and other terpenoids.

β-Carotene is one kind of the most important carotenoids. The major functions of β-carotene include the antioxidant and anti-cardiovascular properties, which make it a growing market. Recently, the use of metabolic engineering to construct microbial cell factories to synthesize β-carotene has become the latest model for its industrial production. Among these cell factories, yeasts including Saccharomyces cerevisiae and Yarrowia lipolytica have attracted the most attention because of the: security, mature genetic manipulation tools, high flux toward carotenoids using the native mevalonate pathway and robustness for large-scale fermentation. In this review, the latest strategies for β-carotene biosynthesis, including protein engineering, promoters engineering and morphological engineering are summarized in detail. Finally, perspectives for future engineering approaches are proposed to improve β-carotene production.

Gibberellic acid (GA3), produced industrially by Fusarium fujikuroi, stands as a crucial plant growth regulator extensively employed in the agriculture filed while limited understanding of the global metabolic network hinders researchers from conducting rapid targeted modifications. In this study, a small-molecule compounds-based targeting technology was developed to increase GA3 production. Firstly, various small molecules were used to target key nodes of different pathways and the result displayed that supplement of terbinafine improved significantly GA3 accumulation, which reached to 1.08 g/L. Subsequently, lipid and squalene biosynthesis pathway were identified as the key pathways influencing GA3 biosynthesis by transcriptomic analysis. Thus, the strategies including in vivo metabolic engineering modification and in vitro supplementation of lipid substrates were adopted, both contributed to an enhanced GA3 yield. Finally, the engineered strain demonstrated the ability to achieve a GA3 yield of 3.24 g/L in 5 L bioreactor when utilizing WCO as carbon source and feed., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Gibberellic acid (GA3) is a vital plant growth hormone widely used in agriculture. Currently, GA3 production relies on liquid fermentation by the filamentous fungus Fusarium fujikuroi . However, the lack of an effective selection marker recycling system hampers the application of metabolic engineering technology in F. fujikuroi , as multiple-gene editing and positive-strain screening still rely on a limited number of antibiotics. In this study, we developed a strategy using pyr4-blaster and CRISPR/Cas9 tools for recycling orotidine-5'-phosphate decarboxylase (Pyr4) selection markers. We demonstrated the effectiveness of this method for iterative gene integration and large gene-cluster deletion. We also successfully improved GA3 titers by overexpressing geranylgeranyl pyrophosphate synthase and truncated 3-hydroxy-3-methyl glutaryl coenzyme A reductase, which rewired the GA3 biosynthesis pathway. These results highlight the efficiency of our established system in recycling selection markers during iterative gene editing events. Moreover, the selection marker recycling system lays the foundation for further research on metabolic engineering for GA3 industrial production., Competing Interests: The authors declare that there is no conflict of interest in the publication of this manuscript., (© 2024 The Authors.)

Metabolic Engineering of yeast is a critical approach to improving the production capacity of cell factories. To obtain genetically stable recombinant strains, the exogenous DNA is preferred to be integrated into the genome. Previously, we developed a Golden Gate toolkit YALIcloneNHEJ, which could be used as an efficient modular cloning toolkit for the random integration of multigene pathways through the innate non-homologous end-joining repair mechanisms of Yarrowia lipolytica. We expanded the toolkit by designing additional building blocks of homologous arms and using CRISPR technology. The reconstructed toolkit was thus entitled YALIcloneHR and designed for gene-specific knockout and integration. To verify the effectiveness of the system, the gene PEX10 was selected as the target for the knockout. This system was subsequently applied for the arachidonic acid production, and the reconstructed strain can accumulate 4.8% of arachidonic acid. The toolkit will expand gene editing technology in Y. lipolytica, which would help produce other chemicals derived from acetyl-CoA in the future., (© 2023. The Author(s), under exclusive licence to Springer Nature B.V.)

Liquid fermentation is the primary method for GA 3 production using Fusarium fujikuroi . However, production capacity is limited due to unknown metabolic pathways. To address this, we constructed a genome-scale metabolic model ( i CY1235) with 1753 reactions, 1979 metabolites, and 1235 genes to understand the GA 3 regulation mechanisms. The model was validated by analyzing growth rates under different glucose uptake rates and identifying essential genes. We used the model to optimize fermentation conditions, including carbon sources and dissolved oxygen. Through the OptForce algorithm, we identified 20 reactions as targets. Overexpressing FFUJ_02053 and FFUJ_14337 resulted in a 37.5 and 75% increase in GA3 titers, respectively. These targets enhance carbon flux toward GA 3 production. Our model holds promise for guiding the metabolic engineering of F. fujikuroi to achieve targeted overproduction. In summary, our study utilizes the i CY1235 model to understand GA 3 regulation, optimize fermentation conditions, and identify specific targets for enhancing GA 3 production through metabolic engineering.

Adaptive laboratory evolution is an innovative approach utilized by researchers to enhance the characteristics of microorganisms in the field of biology. With the advancement of this technology, it is now being extended to non-model strains. Yarrowia lipolytica, an oleaginous yeast with significant industrial potential, stands out among the non-conventional fungi. However, the activity of Yarrowia lipolytica is frequently affected by specific substances and environmental factors, necessitating the development of techniques to address these challenges. This manuscript provides an overview of adaptive laboratory evolution experiments conducted on Yarrowia lipolytica, and categorizes the contents into two aspects including improving lignocellulose utilization and enhancing the production in Yarrowia lipolytica. Additionally, we selected several representative examples to illustrate how adaptive laboratory evolution can be combined with other techniques to elucidate the potential mechanisms underlying strain evolution. Lastly, we anticipate a promising future for adaptive laboratory evolution technology and Yarrowia lipolytica in tandem., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Patchoulol is an important sesquiterpene alcohol with a strong and lasting odor, which has led to prominent applications in perfumes and cosmetics. In this study, systematic metabolic engineering strategies were adopted to create an efficient yeast cell factory for patchoulol overproduction. First, a baseline strain was constructed by selecting a highly active patchoulol synthase. Subsequently, the mevalonate precursor pool was expanded to boost patchoulol synthesis. Moreover, a method for downregulating squalene synthesis based on Cu 2+ -repressible promoter was optimized, which significantly improved the patchoulol titer by 100.9% to 124 mg/L. In addition, a protein fusion strategy resulted in a final titer of 235 mg/L in shake flasks. Finally, 2.864 g/L patchoulol could be produced in a 5 L bioreactor, representing a remarkable 1684-fold increase compared to the baseline strain. To our knowledge, this is the highest patchoulol titer reported so far.

Background: α-Humulene is an important biologically active sesquiterpene, whose heterologous production in microorganisms is a promising alternative biotechnological process to plant extraction and chemical synthesis. In addition, the reduction of production expenses is also an extremely critical factor in the sustainable and industrial production of α-humulene. In order to meet the requirements of industrialization, finding renewable substitute feedstocks such as low cost or waste substrates for terpenoids production remains an area of active research., Results: In this study, we investigated the feasibility of peroxisome-engineering strain to utilize waste cooking oil (WCO) for high production of α-humulene while reducing the cost. Subsequently, transcriptome analysis revealed differences in gene expression levels with different carbon sources. The results showed that single or combination regulations of target genes identified by transcriptome were effective to enhance the α-humulene titer. Finally, the engineered strain could produce 5.9 g/L α-humulene in a 5-L bioreactor., Conclusion: To the best of our knowledge, this is the first report that converted WCO to α-humulene in peroxisome-engineering strain. These findings provide valuable insights into the high-level production of α-humulene in Y. lipolytica and its utilization in WCO bioconversion., (© 2022. The Author(s).)

Arachidonic acid is an essential ω-6 polyunsaturated fatty acid, which plays a significant role in cardiovascular health and neurological development, leading to its wide use in the food and pharmaceutical industries. Traditionally, ARA is obtained from deep-sea fish oil. However, this source is limited by season and is depleting the already threatened global fish stocks. With the rapid development of synthetic biology in recent years, oleaginous fungi have gradually attracted increasing attention as promising microbial sources for large-scale ARA production. Numerous advanced technologies including metabolic engineering, dynamic regulation of fermentation conditions, and multiomics analysis were successfully adapted to increase ARA synthesis. This review summarizes recent advances in the bioengineering of oleaginous fungi for ARA production. Finally, perspectives for future engineering approaches are proposed to further improve the titer yield and productivity of ARA.

Gibberellic acid (GA3) is a plant growth hormone that plays an important role in the production of crops, fruits, and vegetables with a wide market share. Due to intrinsic advantages, liquid fermentation of Fusarium fujikuroi has become the sole method for industrial GA3 production, but the broader application of GA3 is hindered by low titer. In this study, we combined atmospheric and room-temperature plasma (ARTP) with ketoconazole-based screening to obtain the mutant strain 3-6-1 with high yield of GA3. Subsequently, the medium composition and fermentation parameters were systematically optimized to increase the titer of GA3, resulting in a 2.5-fold increase compared with the titer obtained under the initial conditions. Finally, considering that the strain is prone to substrate inhibition and glucose repression, a new strategy of fed-batch fermentation was adopted to increase the titer of GA3 to 575.13 mg/L, which was 13.86% higher than the control. The strategy of random mutagenesis combined with selection and fermentation optimization developed in this study provides a basis for subsequent research on the industrial production of GA3., (© 2022. The Author(s).)

Unusual fatty acids with special carbon chain length or functional groups have been extensively used in the chemical, material, nutraceutical, and pharmaceutical industries. The traditional sources of these valuable fatty acids mainly include animal or plant extraction and chemical synthesis, which are unsustainable and may cause considerable environmental issues. The advancement of synthetic biology tools has facilitated the microbial production of lipids enriched in these fatty acids. The oleaginous yeast Yarrowia lipolytica is considered an attractive industrial host suitable for the production of advanced unusual fatty acids due to its high intrinsic lipogenesis ability. In this review, we introduce the most cutting-edge developments in synthetic biology tools for Y. lipolytica, as well as the recent progress in harnessing these tools to engineer the Y. lipolytica chassis to overaccumulate various unusual fatty acids, including odd-chain fatty acids, conjugated fatty acids, polyunsaturated fatty acids, cyclopropane fatty acids, methyl-branched fatty acids, hydroxylated fatty acids, and medium chain fatty acids. In addition, the future prospects of the unusual fatty acids using the Y. lipolytica platform are discussed in light of the current progress, challenges, and trends in this field. Finally, guidelines for future studies are also emphasized., (Copyright © 2022 Elsevier Inc. All rights reserved.)

The sesquiterpene α-humulene is an important plant natural product, which has been used in the pharmaceutical industry due to its anti-inflammatory and anticancer activities. Although phytoextraction and chemical synthesis have previously been applied in α-humulene production, the low efficiency and high costs limit the development. In this study, Yarrowia lipolytica was engineered as the robust cell factory for sustainable α-humulene production. First, a chassis with high α-humulene output in the cytoplasm was constructed by integrating α-humulene synthases with high catalytic activity, optimizing the flux of mevalonate and acetyl-CoA pathways. Subsequently, the strategy of dual cytoplasmic-peroxisomal engineering was adopted in Y. lipolytica; the best strain GQ3006 generated by introducing 31 copies of 12 different genes could produce 2280.3± 38.2 mg/l (98.7 ± 4.2 mg/g dry cell weight) α-humulene, a 100-fold improvement relative to the baseline strain. To further improve the titer, a novel strategy for downregulation of squalene biosynthesis based on Cu 2+ -repressible promoters was firstly established, which significantly improved the α-humulene titer by 54.2% to 3516.6 ± 34.3 mg/l. Finally, the engineered strain could produce 21.7 g/l α-humulene in a 5-L bioreactor, 6.8-fold higher than the highest α-humulene titer reported before this study. Overall, system metabolic engineering strategies used in this study provide a valuable reference for the highly sustainable production of terpenoids in Y. lipolytica., (© 2022 Wiley Periodicals LLC.)

Microbial production of value-added chemicals derived from fatty acids is a sustainable alternative to petroleum-derived chemicals and unsustainable lipids from animals and plants. Fatty acids with different carbon chain lengths including short- (C20), with either even or odd number of carbons, have significantly different characteristics and wide applications in energy, material, medicine, and nutrition. Tailoring chain-length specificity of these compounds using metabolic engineering would be of high interest. Yarrowia lipolytica , as an oleaginous yeast, is a superior industrial chassis for the production of tailored chain-length fatty acids and their derivatives due to its hyper-oil-producing capability. In this Review, we cover metabolic engineering approaches that can lead to fatty acid chain length control in this microorganism. These approaches involve the manipulation of the fatty acid synthase, the thioesterase, the β-oxidation pathway, the elongation and desaturation pathway, the polyketide synthase-like polyunsaturated fatty acid synthase pathway, and the odd-chain fatty acids synthesis pathway. Finally, we also discuss alternative strategies that can be used in the future to tailored chain-length control.

Terpenes are a large class of secondary metabolites with diverse structures and functions that are commonly used as valuable raw materials in food, cosmetics, and medicine. With the development of metabolic engineering and emerging synthetic biology tools, these important terpene compounds can be sustainably produced using different microbial chassis. Currently, yeasts such as Saccharomyces cerevisiae and Yarrowia lipolytica have received extensive attention as potential hosts for the production of terpenes due to their clear genetic background and endogenous mevalonate pathway. In this review, we summarize the natural terpene biosynthesis pathways and various engineering strategies, including enzyme engineering, pathway engineering, and cellular engineering, to further improve the terpene productivity and strain stability in these two widely used yeasts. In addition, the future prospects of yeast-based terpene production are discussed in light of the current progress, challenges, and trends in this field. Finally, guidelines for future studies are also emphasized.

Due to their vital physiological functions, nutritional fatty acids have great potential as nutraceutical food supplements for preventing an array of diseases such as inflammation, depression, arthritis, osteoporosis, diabetes and cancer. Microbial biosynthesis of fatty acids follows the trend of sustainable development, as it enables green, environmentally friendly and efficient production. As a natural oleaginous yeast, Yarrowia lipolytica is especially well-suited for the production of fatty acids. Moreover, it has a variety of genetic engineering tools and novel metabolic engineering strategies that make it a robust workhorse for the production of an array of value-added products. In this review, we summarize recent advances in metabolic engineering strategies for accumulating nutritional fatty acids in Y. lipolytica , including conjugated fatty acids and polyunsaturated fatty acids. In addition, the future prospects of nutritional fatty acid production using the Y. lipolytica platform are discussed in light of the current progress, challenges, and trends in this field. Finally, guidelines for future studies are also emphasized., Competing Interests: We declare that we have no financial and personal relationships with other people or organizations that can inappropriately influence our work, there is no professional or other personal interest of any nature or kind in any product, service and/or company that could be construed as influencing the position presented in, or the review of, the manuscript entitled, “Engineering Yarrowia lipolytica to produce nutritional fatty acids: Current status and future perspectives”., (© 2022 The Authors.)

Oleic acid is widely applied in the chemical, material, nutritional, and pharmaceutical industries. However, the current production of oleic acid via high oleic plant oils is limited by the long growth cycle and climatic constraints. Moreover, the global demand for high oleic plant oils, especially the palm oil, has emerged as the driver of tropical deforestation causing tropical rainforest destruction, climate change, and biodiversity loss. In the present study, an alternative and sustainable strategy for high oleic oil production was established by reprogramming the metabolism of the oleaginous yeast Yarrowia lipolytica using a two-layer "push-pull-block" strategy. Specifically, the fatty acid synthesis pathway was first engineered to increase oleic acid proportion by altering the fatty acid profiles. Then, the content of storage oils containing oleic acid was boosted by engineering the synthesis and degradation pathways of triacylglycerides. The strain resulting from this two-layer engineering strategy produced the highest titer of high oleic microbial oil reaching 56 g/L with 84% oleic acid in fed-batch fermentation, representing a remarkable improvement of a 110-fold oil titer and 2.24-fold oleic acid proportion compared with the starting strain. This alternative and sustainable method for high oleic oil production shows the potential of substitute planting.

Non-homologous end-joining (NHEJ)-mediated random integration in Yarrowia lipolytica has been demonstrated to be an effective strategy for screening hyperproducer strains. However, there was no multigene assembly method applied for NHEJ integration, which made it challenging to construct and integrate metabolic pathways. In this study, a Golden Gate modular cloning system (YALIcloneNHEJ) was established to develop a robust DNA assembly platform in Y. lipolytica . By optimizing key factors, including the amounts of ligase and the reaction cycles, the assembly efficiency of 4, 7, and 10 fragments reached up to 90, 75, and 50%, respectively. This YALIcloneNHEJ system was subsequently applied for the overproduction of the sesquiterpene (-)-α-bisabolol by constructing a biosynthesis route and enhancing the flux in the mevalonate pathway. The resulting strain produced 4.4 g/L (-)-α-bisabolol, the highest titer reported in yeast to date. Our study expands the toolbox of metabolic engineering and is expected to enable a highly efficient production of various terpenoids., Competing Interests: Z-KN was employed by Jiangxi New Reyphon Biochemical Co., Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Li, Yang, Shen, Peng, Guo, Nie, Sun, Shi, Ji and Huang.)

Yarrowia lipolytica is recognized as an excellent non-conventional yeast in the field of biomanufacturing, where it is used as a host to produce oleochemicals, terpenes, organic acids, polyols and recombinant proteins. Consequently, metabolic engineering of this yeast is becoming increasingly popular to advance it as a superior biomanufacturing platform, of which promoters are the most basic elements for tuning gene expression. Endogenous promoters of Yarrowia lipolytica were reviewed, which are the basis for promoter engineering. The engineering strategies, such as hybrid promoter engineering, intron enhancement promoter engineering, and transcription factor-based inducible promoter engineering are described. Additionally, the applications of Yarrowia lipolytica promoter engineering to rationally reconstruct biosynthetic gene clusters and improve the genome-editing efficiency of the CRISPR-Cas systems were reviewed. Finally, research needs and future directions for promoter engineering are also discussed in this review., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Escherichia coli BL21 (DE3) is the most widely used host for recombinant protein expression. However, not every protein can be highly expressed in BL21 (DE3), so individual optimization strategies are often required for different proteins, which is time-consuming and difficult to apply rapidly for industrial production. Constructing more hosts is a good choice to enrich protein expression selection. The expression level of T7 RNAP is the core control node of the pET expression system, so regulating its expression level is an effective way of improving the production of difficult-to-express proteins. Various BL21 (DE3)-derived variant hosts with different translation levels of T7 RNAP could be obtained by changing the ribosomal binding site (RBS) sequences of T7 RNAP in a genome. Here, a BL21 (DE3)-derived variant strain library with different RBS sequences of T7 RNAP was constructed using a base editor and CRISPR-Cas9. Notably, the CRISPR-Cas9 system combined with degenerate primers enabled the construction of an RBS library with 87.5% of the theoretical coverage in single editing, which is more convenient and efficient than the use of a base editor. The expression level of a target gene in the variant strain library ranged from 28 to 220% of the parental strain. Furthermore, a high-throughput host-screening platform for recombinant protein production was constructed, which enabled us to obtain the best expression host for certain target proteins in only 3 days. As a proof of concept, the production of all eight difficult-to-express proteins was greatly improved, including autolytic protein, membrane proteins, antimicrobial peptides, and hardly soluble proteins. Among them, the expression of glucose dehydrogenase in the best host exhibited a 298-fold increase compared to the parental strain. This strategy is simple and effective, requires no advanced equipment, and can be carried out in any laboratory.

Plasmodium vivax apical membrane antigen-1 (PvAMA-1) is an important vaccine candidate for vivax malaria. However, antigenic variation within PvAMA-1 is a major obstacle to the design of a global protective malaria vaccine. In this study, we analyzed the genetic polymorphism and selection of the PvAMA-1 gene from 152 P. vivax isolates from imported cases to China, collected in the China-Myanmar border (CMB) area in Yunnan Province (YP) during 2009-2011 ( n = 71) and 2014-2016 ( n = 81), in comparison with PvAMA-1 gene information from Myanmar ( n = 73), collected from public data. The overall nucleotide diversity of the PvAMA-1 gene from the 152 YP isolates was 0.007 with 76 haplotypes identified ( Hd = 0.958). Results from the population structure suggested three groups among the YP and Myanmar isolates with optimized clusters value of K = 7. In addition, YP (2014-2016) isolates generally lacked some K components that were commonly found in YP (2009-2011) and Myanmar. Meanwhile, PvAMA-1 domain I is found to be the dominant target of positive diversifying selection and most mutation loci were found in this domain. The mutation frequencies of D107N/A, R112K/T, K120R, E145A, E277K, and R438H in PvAMA-1 were more than 70% in the YP isolates. In conclusion, high genetic diversity and positive selection were found in the PvAMA-1 gene from YP isolates, which are significant findings for the design and development of PvAMA-1-based malaria vaccine., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Cui, Shen, Chen, Kassegne, Shi, Xu, Chen, Wu and Wang.)

Schizochytrium sp. HX-308 is a marine microalga with fast growth and high lipid content, which has potential as microbial cell factories for lipid compound biosynthesis. It is significant to develop efficient genetic editing tool and discover molecular target in Schizochytrium sp. HX-308 for lipid compound biosynthesis. In this study, we developed an efficient gene editing tool in HX-308 which was mediated by Agrobacterium tumefaciens AGL-1. Results showed that the random integration efficiency reached 100%, and the homologous recombination efficiency reached about 30%. Furthermore, the metabolic pathway of lipid and terpenoid biosynthesis were engineered. Firstly, the acetyl-CoA c -acetyltransferase was overexpressed in HX-308 with a strong constitutive promoter. With the overexpression of acetyl-CoA c-acetyltransferase, more acetyl-CoA was used to synthesize terpenoids, and the production of squalene, β-carotene and astaxanthin was increased 5.4, 1.8, and 2.4 times, respectively. Interestingly, the production of saturated fatty acids and polyunsaturated fatty acids also changed. Moreover, three Acyl-CoA oxidase genes which catalyze the first step of β-oxidation were knocked out using homologous recombination. Results showed that the production of lipids increased in the three knock-out strains. Our results demonstrated that the A. tumefaciens -mediated transformation method will be of great use for the study of function genes, as well as developing Schizochytrium sp. as a strong cell factory for producing high value products., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Huang, Xu, Sun, Shi, Gu, Ye and Huang.)

Malaria incidence has declined dramatically over the past decade and China was certified malaria-free in 2021. However, the presence of malaria in border areas and the importation of cases of malaria parasites are major challenges for the consolidation of the achievements made by China. Plasmodium vivax Duffy binding protein (PvDBP) performs a significant role in erythrocyte invasion, and is considered a promising P. vivax vaccine. However, the highly polymorphic region of PvDBP (PvDBP-II) impedes the development of blood-stage vaccine against P. vivax . In this study, we investigated the genetic diversity and natural selection of PvDBP-II among 124 P. vivax isolates collected from the China-Myanmar border (CMB) in Yunnan Province, China, during 2009-2011. To compare genetic diversity, natural selection, and population structure with CMB isolates, 85 pvdbp- II sequences of eastern Myanmar isolates were obtained from GenBank. In addition, global sequences of pvdbp -II were retrieved from GenBank to establish genetic differentiation relationships and networks with the CMB isolates. In total, 22 single nucleotide polymorphisms reflected in 20 non-synonymous and two synonymous mutations were identified. The overall nucleotide diversity of PvDBP-II from the 124 CMB isolates was 0.0059 with 21 haplotypes identified ( Hd = 0.91). The high ratio of non-synonymous to synonymous mutations suggests that PvDBP-II had evolved under positive selection. Population structure analysis of the CMB and eastern Myanmar isolates were optimally grouped into five sub-populations ( K = 5). Polymorphisms of PvDBP-II display that CMB isolates were genetically diverse. Mutation, recombination, and positive selection promote polymorphism of PvDBP-II of P. vivax population. Although low-level genetic differentiation in eastern Myanmar was identified along with the more effective malaria control measures, the complexity of population structure in malaria parasites has maintained. In conclusion, findings from this study advance knowledge of the understanding of the dynamic of P. vivax population, which will contribute to guiding the rational design of a PvDBP-II based vaccine., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Shi, Shen, Chen, Kassegne, Cui, Xu, Chen, Zheng and Wang.)

The sesquiterpene α-humulene has been shown to have anti-inflammatory and anticancer activities, which has led to its vast application potential in medicine. However, α-humulene production methods including phytoextraction and chemical synthesis currently were limited to low yield, high costs, and expensive catalysts, which cannot meet the increasing market demand. In this study, Yarrowia lipolytica was developed as a robust cell factory for α-humulene production. The peroxisome in Y. lipolytica was first engineered to boost the synthesis of the sesquiterpene α-humulene. By compartmentalization of the α-humulene biosynthesis pathway, improving ATP and acetyl-CoA supply, and optimizing the gene copy numbers of rate-limiting enzymes, the engineered strain GQ2012 could produce 3.2 g/L α-humulene in a 5 L bioreactor, the highest α-humulene titer reported so far. Our study provides a valuable reference for highly sustainable production of terpenoids by peroxisome engineering in Y. lipolytica .

Saccharomyces cerevisiae is a widely used microorganism and a greatly popular cell factory for the production of various chemicals. In order to improve the yield of target chemicals, it is often necessary to increase the copy numbers of key genes or engineer the related metabolic pathways, which traditionally required time-consuming repetitive rounds of gene editing. With the development of gene-editing technologies such as meganucleases, TALENs, and the CRISPR/Cas system, multiplex genome editing has entered a period of rapid development to speed up cell factory optimization. Multi-copy insertion and removing bottlenecks in biosynthetic pathways can be achieved through gene integration and knockout, for which multiplexing can be accomplished by targeting repetitive sequences and multiple sites, respectively. Importantly, the development of the CRISPR/Cas system has greatly increased the speed and efficiency of multiplex editing. In this review, the various multiplex genome editing technologies in S. cerevisiae were summarized, and the principles, advantages, and the disadvantages were analyzed and discussed. Finally, the practical applications and future prospects of multiplex genome editing were discussed. KEY POINTS: • The development of multiplex genome editing in S. cerevisiae was summarized. • The pros and cons of various multiplex genome editing technologies are discussed. • Further prospects on the improvement of multiplex genome editing are proposed.

As fungus-like protists, thraustochytrids have been increasingly studied for their faster growth rates and high lipid content. In the 1990s, thraustochytrids were used as docosahexaenoic acid (DHA) producers for the first time. Thraustochytrids genera, such as Thraustochytrium, Schizochytrium, and Aurantiochytrium have been developed and patented as industrial strains for DHA production. The high DHA yield is attributed to its unique and efficient polyketide-like synthase (PKS) pathway. Moreover, thraustochytrids possess a completed mevalonate (MVA) pathway, so it can be used as host for terpenoid production. In order to improve strain performance, the metabolic engineering strategies have been applied to promote or disrupt intracellular metabolic pathways, such as genetic engineering and addition of chemical activators. However, it is difficult to realize industrialization only by improving strain performance. Various operation strategies were developed to enlarge the production quantities from the laboratory-scale, including two-stage cultivation strategies, scale-up technologies and bioreactor design. Moreover, an economical and effective downstream process is also an important consideration for the industrial application of thraustochytrids. Downstream costs accounts for 20-60% of the overall process costs, which represents an attractive target for increasing the cost-competitiveness of thraustochytrids, including how to improve the efficiency of lipid extraction and the further application of biomass residues. This review aims to overview the whole lipid biotechnology of thraustochytrids to provide the background information for researchers., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Terpenoids are an important class of secondary metabolites that play an important role in food, agriculture, and other fields. Microorganisms are rapidly emerging as a promising source for the production of terpenoids. As an oleaginous yeast, Yarrowia lipolytica contains a high lipid content which indicates that it must produce high amounts of acetyl-CoA, a necessary precursor for the biosynthesis of terpenoids. Y. lipolytica has a complete eukaryotic mevalonic acid (MVA) pathway but it has not yet seen commercial use due to its low productivity. Several metabolic engineering strategies have been developed to improve the terpenoids production of Y. lipolytica , including developing the orthogonal pathway for terpenoid synthesis, increasing the catalytic efficiency of terpenoids synthases, enhancing the supply of acetyl-CoA and NADPH, expressing rate-limiting genes, and modifying the branched pathway. Moreover, most of the acetyl-CoA is used to produce lipid, so it is an effective strategy to strike a balance of precursor distribution by rewiring the lipid biosynthesis pathway. Lastly, the latest developed non-homologous end-joining strategy for improving terpenoid production is introduced. This review summarizes the status and metabolic engineering strategies of terpenoids biosynthesis in Y. lipolytica and proposes new insights to move the field forward.

Initial malarial infection mostly causes symptomatic illness in humans. Infection that is not fatal induces complete protection from severe illness and death, and thus complete protection from severe illness or death is granted with sufficient exposure. However, malaria parasite immunity necessitates constant exposure. Therefore, it is important to evaluate lowered immunity and recurrent susceptibility to symptomatic disease in lower transmission areas. We aimed to investigate selection pressure based on transmission levels, antimalarial drug use, and environmental factors. We whole genome sequenced (WGS) P. falciparum clinical samples from Chinese hosts working in Ghana and compared the results with the WGS data of isolates from native Ghanaians downloaded from pf3k. The P. falciparum samples were generally clustered according to their geographic origin, and Chinese imported samples showed a clear African origin with a slightly different distribution from the native Ghanaian samples. Moreover, samples collected from two host populations showed evidence of differences in the intensity of selection. Compared with native Ghanaian samples, the China-imported isolates exhibited a higher proportion of monoclonal infections, and many genes associated with RBC invasion and immune evasion were found to be under less selection pressure. There was no significant difference in the selection of drug-resistance genes due to a similar artemisinin-based combination therapy medication profile. Local selection of malarial parasites is considered to be a result of differences in the host immunity or disparity in the transmission opportunities of the host. In China, most P. falciparum infections were imported from Africa, and under these circumstances, distinct local selective pressures may be caused by varying acquired immunity and transmission intensity. This study revealed the impact of host switching on the immune system, and it may provide a better understanding of the mechanisms that enable clinical immunity to malaria., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Shi, Shi, Chen, Cui, Kassegne, Okpeku, Chen and Shen.)

Microalgae can produce high-value-added products such as lipids and carotenoids using light or sugars, and their biosynthesis mechanism can be triggered by various stress conditions. Under nutrient deprivation or environmental stresses, microalgal cells accumulate lipids as an energy-rich carbon storage battery and generate additional amounts of carotenoids to alleviate the oxidative damage induced by stress conditions. Though stressful conditions are unfavorable for biomass accumulation and can induce oxidative damage, stress-based strategies are widely used in this field due to their effectiveness and economy. For the overproduction of different target products, it is required and meaningful to deeply understand the effects and mechanisms of various stress conditions so as to provide guidance on choosing the appropriate stress conditions. Moreover, the underlying molecular mechanisms under stress conditions can be clarified by omics technologies, which exhibit enormous potential in guiding rational genetic engineering for improving lipid and carotenoid biosynthesis., (Copyright © 2020 Shi, Wang, Zhang, Sun and Huang.)

In recent years, eukaryotic microorganisms have been widely applied to offer many solutions for everyday life and have come to play important roles in agriculture, food, health care, and the fine-chemicals industry. However, the complex genetic background and low homologous recombination efficiency have hampered the implementation of large-scale and high-throughput gene editing in many eukaryotic microorganisms. The low efficiency of homologous recombination (HR) not only makes the modification process labor-intensive but also completely precludes the application of many otherwise very useful genome editing techniques. Thus, increasing the efficiency of HR is clearly an enabling technology for basic research and gene editing in eukaryotic microorganisms. In this review, we summarize the current strategies for enhancing the efficiency of HR in eukaryotic microorganisms (particularly yeasts and filamentous fungi), list some small molecules and candidate genes associated with homologous and non-homologous recombination, and briefly discuss the further development prospects of these strategies.

The enzyme FabH catalyzes the initial step of fatty acid biosynthesis that is essential for bacterial survival. Therefore, FabH has been identified as an attractive target for the development of new antibacterial agents. We present here the discovery of a promising new series of Pyrazol-Benzimidazole amides with low toxicity and potent FabH inhibitory. Twenty-seven novel compounds have been synthesized, and all the compounds were characterized by 1 H NMR, 13 C NMR and MS. Afterwards they were evaluated for in-vitro antibacterial activities against E. coli, P. aeruginosa, B. subtilis and S. aureus, along with E. coli FabH inhibition and cytotoxicity test. Some compounds proved to be of low toxicity and potent, especially compound 31 exhibited the most potential to be a new drug with MIC of 0.49-0.98 μg/mL against the tested bacterial strains and IC 50 of 1.22 μM against E. coli FabH. Eight analogues 16, 28, 30, 31, 33, 34, 35 and 36 with low range MIC against wild type Xanthomonas Campestris exhibited no inhibition against FabH-deficient mutant strain, which firmly proved the class of compounds arrived at antibacterial activity via interacting with FabH. In silico ADMET (Absorption, Distribution, Metabolism, Excretion and Toxicity) evaluation also pointed out that these compounds are potential for druggability. Further, effective overall docking scores of all the compounds have been recorded, and docking simulation of compound 31 into E. coli FabH binding pocket has been conducted, where solid binding interactions has been identified., (Copyright © 2019 Elsevier Masson SAS. All rights reserved.)

Terpenoids are a large class of natural compounds based on the C5 isoprene unit, with many biological effects such activity against cancer and allergies, while some also have an agreeable aroma. Consequently, they have received extensive attention in the food, pharmaceutical and cosmetic fields. With the identification and analysis of the underlying natural product synthesis pathways, current microbial-based metabolic engineering approaches have yielded new strategies for the production of highly valuable terpenoids. Yarrowia lipolytica is a non-conventional oleaginous yeast that is rapidly emerging as a valuable host for the production of terpenoids due to its own endogenous mevalonate pathway and high oil production capacity. This review aims to summarize the status and strategies of metabolic engineering for the heterologous synthesis of terpenoids in Y. lipolytica in recent years and proposes new methods aiming towards further improvement of terpenoid production., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Microalgae are arguably the most abundant single-celled eukaryotes and are widely distributed in oceans and freshwater lakes. Moreover, microalgae are widely used in biotechnology to produce bioenergy and high-value products such as polyunsaturated fatty acids (PUFAs), bioactive peptides, proteins, antioxidants and so on. In general, genetic editing techniques were adapted to increase the production of microalgal metabolites. The main genome editing tools available today include zinc finger nucleases (ZFNs), transcriptional activator-like effector nucleases (TALENs), and the clustered regularly interspaced short palindromic repeats (CRISPR)/Cas nuclease system. Due to its high genome editing efficiency, the CRISPR/Cas system is emerging as the most important genome editing method. In this review, we summarized the available literature on the application of CRISPR/Cas in microalgal genetic engineering, including transformation methods, strategies for the expression of Cas9 and sgRNA, the CRISPR/Cas9-mediated gene knock-in/knock-out strategies, and CRISPR interference expression modification strategies.

The filamentous fungus Fusarium fujikuroi is well-known for its production of natural plant growth hormones: a series of gibberellic acids (GAs). Some GAs, including GA1, GA3, GA4, and GA7, are biologically active and have been widely applied in agriculture. However, the low efficiency of traditional genetic tools limits the further research toward making this fungus more efficient and able to produce tailor-made GAs. Here, we established an efficient CRISPR/Cas9-based genome editing tool for F. fujikuroi. First, we compared three different nuclear localization signals (NLS) and selected an efficient NLS from histone H2B (HTB NLS ) to enable the import of the Cas9 protein into the fungal nucleus. Then, different sgRNA expression strategies, both in vitro and different promoter-based in vivo strategies, were explored. The promoters of the U6 small nuclear RNA and 5S rRNA, which were identified in F. fujikuroi, had the highest editing efficiency. The 5S rRNA-promoter-driven genome editing efficiency reached up to 79.2%. What's more, multigene editing was also explored and showed good results. Finally, we used the developed genome editing tool to engineer the metabolic pathways responsible for the accumulation of a series GAs in the filamentous fungus F. fujikuroi, and successfully changed its GA product profile, from GA3 to tailor-made GA4 and GA7 mixtures. Since these mixtures are more efficient for agricultural use, especially for fruit growth, the developed strains will greatly improve industrial GA production.

Tubulin-targeting drugs have increasingly become the focus of anticancer drugs research. Twenty-five novel benzimidazole grafted benzsulfamide-containing pyrazole ring derivatives were synthesized and evaluated for bioactivity as potential tubulin polymerization inhibitors. Among them, compound 30 showed the most excellent inhibition against tubulin assembly (IC 50  = 1.52 μM) and in vitro growth inhibitory activity against a panel of four human cancer cell lines (IC 50  = 0.15, 0.21, 0.33 and 0.17 μM, respectively for A549, Hela, HepG2 and MCF-7). It could also validly induce A549 cell apoptosis, cause cell cycle arrest in G2/M phase and disrupt the cellular microtubule network. These results, along with molecular docking data, provided an important basis for further optimization of compound 30 as a potential anticancer agent., (Copyright © 2018. Published by Elsevier Ltd.)

The oleaginous yeast Yarrowia lipolytica is widely used for the production of both bulk and fine chemicals, including organic acids, fatty acid-derived biofuels and chemicals, polyunsaturated fatty acids, single-cell proteins, terpenoids, and other valuable products. Consequently, it is becoming increasingly popular for metabolic engineering applications. Multiple gene manipulation tools including URA blast, Cre/LoxP, and transcription activator-like effector nucleases (TALENs) have been developed for metabolic engineering in Y. lipolytica. However, the low efficiency and time-consuming procedures involved in these methods hamper further research. The emergence of the CRISPR/Cas system offers a potential solution for these problems due to its high efficiency, ease of operation, and time savings, which can significantly accelerate the genomic engineering of Y. lipolytica. In this review, we summarize the research progress on the development of CRISPR/Cas systems for Y. lipolytica, including Cas9 proteins and sgRNA expression strategies, as well as gene knock-out/knock-in and repression/activation applications. Finally, the most promising and tantalizing future prospects in this area are highlighted.

The beta-hydroxy acid 3-hydroxypropionic acid (3-HP) is an attractive platform compound that can be used as a precursor for many commercially interesting compounds. In order to reduce the dependence on petroleum and follow sustainable development, 3-HP has been produced biologically from glucose or glycerol. It is reported that 3-HP synthesis pathways can be constructed in microbes such as Escherichia coli, Klebsiella pneumoniae and the yeast Saccharomyces cerevisiae . Among these host strains, yeast is prominent because of its strong acid tolerance which can simplify the fermentation process. Currently, the malonyl-CoA reductase pathway and the β-alanine pathway have been successfully constructed in yeast. This review presents the current developments in 3-HP production using yeast as an industrial host. By combining genome-scale engineering tools, malonyl-CoA biosensors and optimization of downstream fermentation, the production of 3-HP in yeast has the potential to reach or even exceed the yield of chemical production in the future.

In recent years, a variety of genetic tools have been developed and applied to various filamentous fungi, which are widely applied in agriculture and the food industry. However, the low efficiency of gene targeting has for many years hampered studies on functional genomics in this important group of microorganisms. The emergence of CRISPR/Cas9 genome-editing technology has sparked a revolution in genetic research due to its high efficiency, versatility, and easy operation and opened the door for the discovery and exploitation of many new natural products. Although the application of the CRISPR/Cas9 system in filamentous fungi is still in its infancy compared to its common use in E. coli, yeasts, and mammals, the deep development of this system will certainly drive the exploitation of fungal diversity. In this review, we summarize the research progress on CRISPR/Cas9 systems in filamentous fungi and finally highlight further prospects in this area.

A series of new 1-phenylsulphonyl-2-(1-methylindol-3-yl)-benzimidazole derivatives were designed, synthesized and evaluated as potential inhibitors of tubulin polymerization and anthropic cancer cell lines. Among them, compound 33 displayed the most potent tubulin polymerization inhibitory activity in vitro (IC 50  = 1.41 μM) and strong antiproliferative activities against A549, Hela, HepG2 and MCF-7 cell lines in vitro with GI 50 value of 1.6, 2.7, 2.9 and 4.3 μM, respectively, comparable with the positive control colchicine (GI 50 value of 4.1, 7.2, 9.5 and 14.5 μM, respectively) and CA-4 (GI 50 value of 2.2, 4.3, 6.4 and 11.4 μM, respectively). Simultaneously, we evaluated that compound 33 could effectively induce apoptosis of A549 associated with G2/M phase cell cycle arrest. Immunofluorescence microscopy also clearly indicated compound 33 a potent antimicrotubule agent. Docking simulation showed that compound 33 could bind tightly with the colchicine-binding site and act as a tubulin inhibitor. Three-dimensional-QSAR model was also built to provide more pharmacophore understanding that could be used to design new agents with more potent tubulin assembling inhibitory activity in the future., (© 2016 John Wiley & Sons A/S.)

Microbial oils, which are mainly extracted from yeasts, molds, and algae, have been of considerable interest as food additives and biofuel resources due to their high lipid content. While these oleaginous microorganisms generally produce only small amounts of lipids under optimal growth conditions, their lipid accumulation machinery can be induced by environmental stresses, such as nutrient limitation and an inhospitable physical environmental. As common second messengers of many stress factors, reactive oxygen species (ROS) may act as a regulator of cellular responses to extracellular environmental signaling. Furthermore, increasing evidence indicates that ROS may act as a mediator of lipid accumulation, which is associated with dramatic changes in the transcriptome, proteome, and metabolome. However, the specific mechanisms of ROS involvement in the crosstalk between extracellular stress signaling and intracellular lipid synthesis require further investigation. Here, we summarize current knowledge on stress-induced lipid biosynthesis and the putative role of ROS in the control of lipid accumulation in oleaginous microorganisms. Understanding such links may provide guidance for the development of stress-based strategies to enhance microbial lipid production.

Plant hormones are a class of organic substances which are synthesized during the plant metabolism. They have obvious physiological effect on plant growth at very low concentrations. Generally, plant hormones are mainly divided into 5 categories: auxins, cytokinins, ethylene, gibberellins (GAs) and abscisic acid (ABA). With the deepening of research, some novel plant hormones such as brassinosteroid and salicylates have been found and identified. The plant hormone products are mainly obtained through plant extraction, chemical synthesis as well as microbial fermentation. However, the extremely low yield in plants and relatively complex chemical structure limit the development of the former 2 approaches. Therefore, more attention has been paid into the microbial fermentative production. In this commentary, the developments and technological achievements of the 2 important plant hormones (GAs and ABA) have been discussed. The discovery, producing strains, fermentation technologies, and their accumulation mechanisms are first introduced. Furthermore, progresses in the industrial mass scale production are discussed. Finally, guidelines for future studies for GAs and ABA production are proposed in light of the current progress, challenges and trends in the field. With the widespread use of plant hormones in agriculture, we believe that the microbial production of plant hormones will have a bright future.

The adsorption behavior of Cd, Co and Zn on nanometer-size TiQ2 was investigated. At pH 9.0, Cd, Co and Zn were retained on the nanometer-size TiO2, then eluted with 0.1 mol x L(-1) HNO3 and determined by ICP-AES. The adsorption capacities of nanometer TiO2 were found to be 8.1, 6.9 and 15.1 mg x g(-1) for Cd, Co and Zn respectively. The detection limits (3sigma) for Cd, Co and Zn are 5.1, 3.4 and 2.9 ng x mL(-1) respectively. The proposed method has been applied to the determination of trace Cd, Co and Zn in environmental samples with satisfactory results.