Expression of the Acremonium chrysogenum cefT gene in Penicillum chrysogenum indicates that it encodes an hydrophilic beta-lactam transporter

Harnessing biotechnology for penicillin production: Opportunities and environmental considerations

Since the discovery of antibiotics, penicillin has remained the top choice in clinical medicine. With continuous advancements in biotechnology, penicillin production has become cost-effective and efficient. Genetic engineering techniques have been employed to enhance biosynthetic pathways, leading to the production of new penicillin derivatives with improved properties and increased efficacy against antibiotic-resistant pathogens. Advances in bioreactor design, media formulation, and process optimization have contributed to higher yields, reduced production costs, and increased penicillin accessibility. While biotechnological advances have clearly benefited the global production of this life-saving drug, they have also created challenges in terms of waste management. Production fermentation broths from industries contain residual antibiotics, by-products, and other contaminants that pose direct environmental threats, while increased global consumption intensifies the risk of antimicrobial resistance in both the environment and living organisms. The current geographical and spatial distribution of antibiotic and penicillin consumption dramatically reveals a worldwide threat. These challenges are being addressed through the development of novel waste management techniques. Efforts are aimed at both upstream and downstream processing of antibiotic and penicillin production to minimize costs and improve yield efficiency while lowering the overall environmental impact. Yield optimization using artificial intelligence (AI), along with biological and chemical treatment of waste, is also being explored to reduce adverse impacts. The implementation of strict regulatory frameworks and guidelines is also essential to ensure proper management and disposal of penicillin production waste. This review is novel because it explores the key remaining challenges in antibiotic development, the scope of machine learning tools such as Quantitative Structure-Activity Relationship (QSAR) in modern biotechnology-driven production, improved waste management for antibiotics, discovering alternative path to reducing antibiotic use in agriculture through alternative meat production, addressing current practices, and offering effective recommendations.

The ABCT31 Transporter Regulates the Export System of Phenylacetic Acid as a Side-Chain Precursor of Penicillin G in Monascus ruber M7

The biosynthesis of penicillin G (PG) is compartmentalized, and the transportation of the end and intermediate products, and substrates (precursors) such as L-cysteine (L-Cys), L-valine (L-Val) and phenylacetic acid (PAA) requires traversing membrane barriers. However, the transportation system of PAA as a side chain of PG are unclear yet. To discover ABC transporters (ABCTs) involved in the transportation of PAA, the expression levels of 38 ABCT genes in the genome of Monascus ruber M7, culturing with and without PAA, were examined, and found that one abct gene, namely abct31, was considerably up-regulated with PAA, indicating that abct31 may be relative with PAA transportation. Furthermore the disruption of abct31 was carried out, and the effects of two PG substrate's amino acids (L-Cys and L-Val), PAA and some other weak acids on the morphologies and production of secondary metabolites (SMs) of Δabct31 and M. ruber M7, were performed through feeding experiments. The results revealed that L-Cys, L-Val and PAA substantially impacted the morphologies and SMs production of Δabct31 and M. ruber M7. The UPLC-MS/MS analysis findings demonstrated that Δabct31 did not interrupt the synthesis of PG in M. ruber M7. According to the results, it suggests that abct31 is involved in the resistance and detoxification of the weak acids, including the PAA in M. ruber M7.

Penicillium chrysogenum, a Vintage Model with a Cutting-Edge Profile in Biotechnology

The discovery of penicillin entailed a decisive breakthrough in medicine. No other medical advance has ever had the same impact in the clinical practise. The fungus Penicillium chrysogenum (reclassified as P. rubens) has been used for industrial production of penicillin ever since the forties of the past century; industrial biotechnology developed hand in hand with it, and currently P. chrysogenum is a thoroughly studied model for secondary metabolite production and regulation. In addition to its role as penicillin producer, recent synthetic biology advances have put P. chrysogenum on the path to become a cell factory for the production of metabolites with biotechnological interest. In this review, we tell the history of P. chrysogenum, from the discovery of penicillin and the first isolation of strains with high production capacity to the most recent research advances with the fungus. We will describe how classical strain improvement programs achieved the goal of increasing production and how the development of different molecular tools allowed further improvements. The discovery of the penicillin gene cluster, the origin of the penicillin genes, the regulation of penicillin production, and a compilation of other P. chrysogenum secondary metabolites will also be covered and updated in this work.

Genetic Modification of mfsT Gene Stimulating the Putative Penicillin Production in Monascus ruber M7 and Exhibiting the Sensitivity towards Precursor Amino Acids of Penicillin Pathway

The biosynthesis of penicillin G (PG) is compartmentalized, which forces penicillin and its intermediates to cross the membrane barriers. Although many aspects around the penicillin intermediates traffic system remain unclosed, the transmembrane transporter protein involvement has been only predicted. In the present work, detection of PG and isopenicillin N (IPN) in Monascus ruber M7 was performed and functions of mfst gene as a transporter were investigated by the combination of gene deletion (Δmfst) complementation (ΔmfsT::mfsT) and overexpression (M7::PtrpC-mfsT). While, the feeding of PG pathway precursor side chain and amino acids, i.e., phenylacetic acid, D-valine, and L-cysteine was performed for the interpretation of mfsT gene role as an intermediate transporter. The results showed that, the feeding of phenylacetic acid, D-valine, and L-cysteine possessed a significant effect on morphologies, secondary metabolites (SMs) production of all above-mentioned strains including M. ruber M7. The results of UPLC-MS/MS revealed that, ΔmfsT interrupt the penicillin G (PG) production in M. ruber M7 by blocking the IPN transportation, while PG and IPN produced by the ΔmfsT::mfsT have been recovered the similar levels to those of M. ruber M7. Conclusively, these findings suggest that the M. ruber M7 is, not only a PG producer, but also, indicate that the mfsT gene is supposed to play a key role in IPN intermediate compound transportation during the PG production in M. ruber M7.

Pathway transfer in fungi

Itaconic acid is an important building block for the chemical industry. Currently, Aspergillus terreus is the main organism used for itaconic acid production. Due to the enormous citric acid production capacity of Aspergillus niger, this host is investigated as a potential itaconic acid production host. Several strategies have been tried so far: fermentation optimization, expression of cis-aconitate decarboxylase (cadA) alone and in combination with aconitase targeted to the same compartment, chassis optimization, and the heterologous expression of two transporters flanking the cadA gene. We showed that the heterologous expression of these two transporters were key to improving itaconic acid production in an A. niger strain that was unable to produce oxalic acid and gluconic acid. The expression of transporters has increased the production levels of other industrially relevant processes as well, such as β-lactam antibiotics and bioethanol. Thus far, the role of transporters in production process optimization is a bit overlooked.

The transport of phenylacetic acid across the peroxisomal membrane is mediated by the PaaT protein in Penicillium chrysogenum

Penicillium chrysogenum, an industrial microorganism used worldwide for penicillin production, is an excellent model to study the biochemistry and the cell biology of enzymes involved in the synthesis of secondary metabolites. The well-known peroxisomal location of the last two steps of penicillin biosynthesis (phenylacetyl-CoA ligase and isopenicillin N acyltransferase) requires the import into the peroxisomes of the intermediate isopenicillin N and the precursors phenylacetic acid and coenzyme A. The mechanisms for the molecular transport of these precursors are still poorly understood. In this work, a search was made, in the genome of P. chrysogenum, in order to find a Major Facilitator Superfamily (MFS) membrane protein homologous to CefT of Acremonium chrysogenum, which is known to confer resistance to phenylacetic acid. The paaT gene was found to encode a MFS membrane protein containing 12 transmembrane spanners and one Pex19p-binding domain for Pex19-mediated targeting to peroxisomal membranes. RNA interference-mediated silencing of the paaT gene caused a clear reduction of benzylpenicillin secretion and increased the sensitivity of P. chrysogenum to the penicillin precursor phenylacetic acid. The opposite behavior was found when paaT was overexpressed from the glutamate dehydrogenase promoter that increases phenylacetic acid resistance and penicillin production. Localization studies by fluorescent laser scanning microscopy using PaaT-DsRed and EGFP-SKL fluorescent fusion proteins clearly showed that the protein was located in the peroxisomal membrane. The results suggested that PaaT is involved in penicillin production, most likely through the translocation of side-chain precursors (phenylacetic acid and phenoxyacetic acid) from the cytosol to the peroxisomal lumen across the peroxisomal membrane of P. chrysogenum.

Characterization of a novel peroxisome membrane protein essential for conversion of isopenicillin N into cephalosporin C

The mechanisms of compartmentalization of intermediates and secretion of penicillins and cephalosporins in β-lactam antibiotic-producing fungi are of great interest. In Acremonium chrysogenum, there is a compartmentalization of the central steps of the CPC (cephalosporin C) biosynthetic pathway. In the present study, we found in the 'early' CPC cluster a new gene named cefP encoding a putative transmembrane protein containing 11 transmembrane spanner. Targeted inactivation of cefP by gene replacement showed that it is essential for CPC biosynthesis. The disrupted mutant is unable to synthesize cephalosporins and secretes a significant amount of IPN (isopenicillin N), indicating that the mutant is blocked in the conversion of IPN into PenN (penicillin N). The production of cephalosporin in the disrupted mutant was restored by transformation with both cefP and cefR (a regulatory gene located upstream of cefP), but not with cefP alone. Fluorescence microscopy studies with an EGFP (enhanced green fluorescent protein)-SKL (Ser-Lys-Leu) protein (a peroxisomal-targeted marker) as a control showed that the red-fluorescence-labelled CefP protein co-localized in the peroxisomes with the control peroxisomal protein. In summary, CefP is a peroxisomal membrane protein probably involved in the import of IPN into the peroxisomes where it is converted into PenN by the two-component CefD1/CefD2 protein system.

Regulation and compartmentalization of β-lactam biosynthesis

Penicillins and cephalosporins are β‐lactam antibiotics widely used in human medicine. The biosynthesis of these compounds starts by the condensation of the amino acids l‐α‐aminoadipic acid, l‐cysteine and l‐valine to form the tripeptide δ‐l‐α‐aminoadipyl‐l‐cysteinyl‐d‐valine catalysed by the non‐ribosomal peptide ‘ACV synthetase’. Subsequently, this tripeptide is cyclized to isopenicillin N that in Penicillium is converted to hydrophobic penicillins, e.g. benzylpenicillin. In Acremonium and in streptomycetes, isopenicillin N is later isomerized to penicillin N and finally converted to cephalosporin. Expression of genes of the penicillin (pcbAB, pcbC, pendDE) and cephalosporin clusters (pcbAB, pcbC, cefD1, cefD2, cefEF, cefG) is controlled by pleitropic regulators including LaeA, a methylase involved in heterochromatin rearrangement. The enzymes catalysing the last two steps of penicillin biosynthesis (phenylacetyl‐CoA ligase and isopenicillin N acyltransferase) are located in microbodies, as shown by immunoelectron microscopy and microbodies proteome analyses. Similarly, the Acremonium two‐component CefD1–CefD2 epimerization system is also located in microbodies. This compartmentalization implies intracellular transport of isopenicillin N (in the penicillin pathway) or isopenicillin N and penicillin N in the cephalosporin route. Two transporters of the MFS family cefT and cefM are involved in transport of intermediates and/or secretion of cephalosporins. However, there is no known transporter of benzylpenicillin despite its large production in industrial strains.