Biology subjects

Sandlin, N.

Publications and source records attributed to Sandlin, N..

4 recordsLinked to original sources

bioRxiv2023

Weakly alkaline conditions degrade aflatoxins through lactone ring opening

Aflatoxins (AFs) are fungal metabolites that ubiquitously contaminate many common food crops and contribute to major foodborne diseases in humans and animals. The ability to remove AFs from common food and feed commodities will improve health standards and limit the economic impact inflicted by AF food contamination. Known chemical strategies have used strong acids and bases to remove contaminating AF, but these methods often lead to ecological waste issues downstream. In this study, we explore the application of weaker acidic and alkaline conditions to removes two types of AFs, AFB1 and AFG2. We find that a pH 9 buffered environment reduces AFB1 and AFG2 by more than 50% and 95%, respectively, within 24 hours. We show that AF degradation is through lactone ring opening, which is a known cause of AF toxicity, and provide a potential structure of the AFG2 degradation byproduct. Further, we confirm that incubation in the pH 9 environment reduces the genotoxicity of AFB1. Our findings indicate that a weakly alkaline environment may adequately detoxify AF-contaminated food or feed without the need to apply stronger or harsher basic conditions.

bioengineering↗

bioRxiv2023

Starch can expedite the screening for bacterial aflatoxin degraders

Aflatoxins (AFs) are secondary fungal metabolites that contaminate common food crops and are harmful to humans and animals. The ability to degrade or remove aflatoxins from common feed commodities will improve health standards and counter the economic drain inflicted by AF contamination. Bioremediation is a promising solution to AF contamination because of its low cost and few undesired environmental side-effects. Identifying new degrader species is highly beneficial in that it can offer alternatives to overcome the limitations of existing biodegraders, such as narrow working conditions and low degradation rates. Here, we screen several environmental isolates for their AF detoxification ability, using aflatoxin G2. We use different carbon sources (glucose and starch) as isolation and culturing media to examine the effect of the environment on degradation ability. Strains isolated in media with starch as the primary carbon source showed a higher percentage of good AF degraders, 16% compared to 2% when glucose was the primary carbon source. Additionally, the majority of species isolated in glucose medium exhibited improved degradation efficiency when moved into starch medium, with one isolate improving degradation levels from 30% to 70%. Our starch screen also revealed three previously unidentified AF degrader bacterial species. Good aflatoxin G2 degraders also appear to perform well against aflatoxin B1. Overall, for AF degradation, starch medium expedites the screening process and generally improves the performance of isolates. We thus propose that using starch as the carbon source is a promising means to identify new AF degraders in the environment.

microbiology↗

bioRxiv2022

Partner-assisted artificial selection of a secondary function for efficient bioremediation

Microbial enzymes have a broad potential to address many current needs, such as detoxification of harmful toxins and waste, but their native performance often does not match specific applications of interest. In attempting to evolve strains for a specific need, one challenge is that our functions of interest may not confer a fitness effect on the producer. As a result, a conventional selection scheme cannot be used to improve such secondary functions. We propose an alternative approach, partner-assisted artificial selection (PAAS), in which an assisting population acts as an intermediate to create a feedback from the function of interest to the fitness of the producer. We use a simplified model to examine how well and under what conditions such a scheme leads to improved enzymatic function, focusing on degradation of a toxin as a case example. We find that selection for improved growth in this scheme successfully leads to improved degradation performance, even in the presence of other sources of stochasticity. We find that standard selection considerations apply in PAAS: a more restrictive bottleneck leads to stronger selection but adds uncertainty. We also examine how much stochasticity in other traits can be tolerated in PAAS. Our findings offer a roadmap for successful implementation of PAAS to evolve improved functions of interest such as detoxification of harmful compounds.

microbiology↗

bioRxiv2021

Enzyme fatigue limits the detoxification of aflatoxin by Rhodococcus species

Bacterial detoxification of mycotoxins has the potential to offer a low-cost solution to ensure that feed and food commodities contaminated by fungal growth become safe to consume. Among bacteria, Rhodococcus species are of particular interest because they can be metabolically versatile, non-pathogenic, and environment-friendly. However, the native response of Rhodococcus environmental isolates appears inadequate for current detoxification needs. By analyzing the detoxification of aflatoxin by two Rhodococcus species: R. pyridinivorans and R. erythropolis, we examine important features of the dynamics that could guide future optimization of bacterial detoxification. Our results for Rhodococcus species suggest that detoxification happens through a regulated process of secreting extracellular enzymes. We show that enzyme fatigue in the presence of the toxin determines the lifetime of the enzyme and limits the overall detoxification performance of these species. Additionally, we show that the regulation of enzyme production can be both species- and environment-dependent. Overall, our quantitative approach reveals that enzyme fatigue is a major determinant of overall detoxification and needs to be accounted for in assessing the performance of detoxification by live cells or cell-free filtrates.

microbiology↗