Institut für Lebensmittelwissenschaft und Biotechnologie

Permanent URI for this collectionhttps://hohpublica.uni-hohenheim.de/handle/123456789/6

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Bioprospecting for novel lipopeptide-producing strains for potential application in food and agriculture
(2024) Akintayo, Stephen Olusanmi; Hausmann, Rudolf
The need for sustainable alternatives to chemical products has been a huge topic in recent years and has put a demand on researchers and biotechnological companies to come up with bio-based alternatives to several chemical products. In line with this, interest in biosurfactants as alternatives to chemical surfactants is on the rise. Biosurfactants produced by microorganisms have great potential for application in detergents, personal care products, and pharmaceuticals, as well as in environmental, food processing, and agricultural applications. There are a few types of biosurfactants, including lipopeptides, which are primarily produced by Bacillus species and exhibit antimicrobial properties in addition to the well-known surface activity, surface tension reduction, and emulsifying ability of biosurfactants. Like other biosurfactants, lipopeptides have found more use in environmental applications such as bioremediation and microbial enhanced oil recovery (MEOR), while their use in agriculture and food industries remains limited due to concerns that may be related to acceptability, compatibility, and low yield by wild-type strains. To overcome these challenges, this thesis sought to find novel wild-type lipopeptide-producing strains from food-related sources that could be presumably safe for use in agriculture and food applications. To achieve this goal, a screening approach that combined several methods was adopted to identify potential high-yield wild-type, and possibly novel lipopeptide-producing strains. The ability of selected strains as promising biocontrol agents in agriculture was also evaluated. In Publication 1, potential lipopeptide-producing strains were isolated from food-related sources and screened for lipopeptide production. The screening approach combined microbiological and molecular identification of strains, with screening methods based on biosurfactant properties, as well as chemical analysis of surfactin production. Strains with promising lipopeptide-production potential belonging to three genera of Bacillus, Lysinibacillus and Priestia were identified. These strains included several exotic species that were either previously unknown or minimally studied with respect to LP production. Multiple strains that produced more than 150 mg L-1 surfactin, including a B. subtilis strain with a yield of about 1.5 g L−1 were discovered. In Publication 2, two promising LP-producing B. velezensis strains ES1-02 and EFSO2-04 were evaluated for their biocontrol potential and compared with commercial biocontrol strains B. velezensis QST713 and FZB42. The isolated strains demonstrated biocontrol ability comparable to QST713 against Diaporthe spp., which are notorious fungal pathogens of soybeans and other economically important crops. Co-incubation of strain ES1-02 with the phytopathogen D. longicolla induced a 10-fold increase in surfactin production. The broader molecular response of B. velezensis to plant pathogens investigated through an associated global proteome analysis showed the adaptation and response mechanisms of B. velezensis to plant pathogens. In general, B. velezensis seemed to adopt LP- modulation, physiological adaptation, and increased abundance of antimicrobial compounds as antagonistic and adaptation strategies for interaction with the phytopathogen D. longicolla. In Publication 3, genomic techniques were used in the discovery and description of a novel lipopeptides-producing species of the genus Lysinibacillus for which the name Lysinibacillus irui sp. nov. was proposed. This Gram-positive, motile, aerobic, rod-shaped, endospore-forming strain designated IRB4-01T was isolated from fermented African locust beans (Iru) and as such was named after Iru. A comprehensive chemotaxonomic analysis of the strain showed that the cell wall peptidoglycan type is A4α (Lys–Asp), and MK-7 is the major respiratory quinone. Detailed information about the polar lipids and major cellular fatty acids was also obtained. The G+C content of the genomic DNA was 37.4 mol%. Surfactin production by this novel strain was described in Publication 1 of this work.
Characterization of Bacillus velezensis UTB96, demonstrating improved lipopeptide production compared to the strain B. velezensis FZB42
(2022) Vahidinasab, Maliheh; Adiek, Isabel; Hosseini, Behnoush; Akintayo, Stephen Olusanmi; Abrishamchi, Bahar; Pfannstiel, Jens; Henkel, Marius; Lilge, Lars; Vögele, Ralf ; Hausmann, Rudolf
Bacillus strains can produce various lipopeptides, known for their antifungal properties. This makes them attractive metabolites for applications in agriculture. Therefore, identification of productive wild-type strains is essential for the development of biopesticides. Bacillus velezensis FZB42 is a well-established strain for biocontrol of plant pathogens in agriculture. Here, we characterized an alternative strain, B. velezensis UTB96, that can produce higher amounts of all three major lipopeptide families, namely surfactin, fengycin, and iturin. UTB96 produces iturin A. Furthermore, UTB96 showed superior antifungal activity towards the soybean fungal pathogen Diaporthe longicolla compared to FZB42. Moreover, the additional provision of different amino acids for lipopeptide production in UTB96 was investigated. Lysine and alanine had stimulatory effects on the production of all three lipopeptide families, while supplementation of leucine, valine and isoleucine decreased the lipopeptide bioproduction. Using a 45-litre bioreactor system for upscaling in batch culture, lipopeptide titers of about 140 mg/L surfactin, 620 mg/L iturin A, and 45 mg/L fengycin were achieved. In conclusion, it becomes clear that B. velezensis UTB96 is a promising strain for further research application in the field of agricultural biological controls of fungal diseases.
Exploration of surfactin production by newly isolated Bacillus and Lysinibacillus strains from food‐related sources
(2022) Akintayo, Stephen Olusanmi; Treinen, Chantal; Vahidinasab, Maliheh; Pfannstiel, Jens; Bertsche, Ute; Fadahunsi, I.; Oellig, Claudia; Granvogl, Michael; Henkel, Marius; Lilge, Lars; Hausmann, Rudolf
As a lipopeptide (LP), surfactin exhibits properties, such as emulsifying and dispersing ability, which are useful in food industry. Discovery of new LP‐producing strains from food sources is an important step towards possible application of surfactin in foods. A total of 211 spore‐forming, Gram‐positive, and catalase‐positive bacterial strains were isolated from fermented African locust beans (iru) and palm oil mill effluents in a screening process and examined for their ability to produce surfactin. This was achieved by a combination of methods, which included microbiological and molecular classification of strains, along with chemical analysis of surfactin production. Altogether, 29 isolates, positive for oil spreading and emulsification assays, were further identified with 16S rDNA analysis. The strains belonged to nine species including less commonly reported strains of Lysinibacillus, Bacillus flexus, B. tequilensis, and B. aryabhattai. The surfactin production was quantitatively and qualitatively analysed by high‐performance thin‐layer chromatography and liquid chromatography‐mass spectrometry (LC–MS). Confirmation of surfactin by MS was achieved in all the 29 strains. Highest surfactin production capability was found in B. subtilis IRB2‐A1 with a titre of 1444·1 mg L−1.

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