Psychrotolerant biosurfactant-producing bacteria for hydrocarbon degradation: a mini review

Biosurfactants are a structurally diverse group of surface-active substances synthesised by microorganisms. All biosurfactants have tremendous potential ranging from medicine to environmental applications especially in hydrocarbon remediation. Petroleum pollution is a major issue in both cold and temperate climate countries. These hydrocarbon pollutants have low solubility and high solid-water distribution ratios, thus limiting the interaction between microbial cells. Petroleum pollution is a major issue in both cold and temperate climate countries. In Antarctica, due to the recalcitrant nature of hydrocarbon components coupled with the region's extremely weather conditions, there were difficulties faced by bioremediation approaches. However, using biosurfactant in hydrocarbon bioremediation increases the bioavailability of hydrocarbon, thus expediting bioremediation. Few studies have reported on psychrotolerant bacterial species that are able to degrade hydrocarbon and produce biosurfactants. This review focuses on psychrotolerant bacteria with the potential to synthesise biosurfactants and degrade hydrocarbons

Prevalence of thyroid disorders in pregnant women in Hospital Tengku Ampuan Afzan & International Islamic University Malaysia Medical Centre

Introduction: Data on the burden of thyroid disease in pregnant women in our community is scarce albeit the detrimental effects it brought to both the mother and fetus if left untreated. The aim of this study was to determine the prevalence of thyroid disorders, socio-demography distribution, and method of diagnosis in pregnant women of both tertiary centres in Kuantan, Pahang. Materials and Methods: A retrospective cross sectional study involving patients under follow ups at the Endocrine and Obstetric Clinics of Hospital Tengku Ampuan Afzan (HTAA) and International Islamic University Malaysia Medical Center (IIUM MC) from the 1st January until the 30th June 2017. Out of 923 pregnant women, 29 were found to have thyroid disorders. Detailed demographic data and thyroid function test readings were taken from their medical records and thyroid status were determined from TSH and FT4 readings using the trimester-specific thyroid reference range. Results: The prevalence of thyroid disorders in both centres was 3.14%, with specific prevalence of 2.80% for HTAA and 6.12% for IIUM MC. Nearly half of them were hyperthyroid (47.85%), 17.4% was hypothyroid and Graves’ disease dominated the diagnosis of thyroid disease (30.43%). Significant association was found in weight changes with patients’ thyroid status; reduction in weight in first trimester and increment in weight in second trimester were mainly seen in the hyperthyroid group (p<0.01, p=0.027). Conclusion: The acceptable prevalence of 3.14% for thyroid disorders in pregnancy could be contributed by the iodine availability in this community. High prevalence of Graves’ disease warrants future screening for maternal thyroid stimulating immunoglobulin amongst hyperthyroid women

Response surface methodology optimisation and kinetics of diesel degradation by a cold-adapted Antarctic bacterium, Arthrobacter sp. strain AQ5-05

Petroleum hydrocarbons, notably diesel oil, are the main energy source for running amenities in the Antarctic region and are the major cause of pollution in this area. Diesel oil spills are one of the major challenges facing management of the Antarctic environment. Bioremediation using bacteria can be an effective and eco-friendly approach for their remediation. However, since the introduction of non-native organisms, including microorganisms, into the Antarctic or between the distinct biogeographical regions within the continent is not permitted under the Antarctic Treaty, it is crucial to discover native oil-degrading, psychrotolerant microorganisms that can be used in diesel bioremediation. The primary aim of the current study is to optimize the conditions for growth and diesel degradation activity of an Antarctic local bacterium, Arthrobacter sp. strain AQ5-05, using the Plackett-Burman approach and response surface method (RSM) via a central composite design (CCD) approach. Based on this approach, temperature, pH, and salinity were calculated to be optimum at 16.30 °C, pH 7.67 and 1.12% (w/v), respectively. A second order polynomial regression model very accurately represented the experimental figures’ interpretation. These optimized environmental conditions increased diesel degradation from 34.5% (at 10 °C, pH 7.00 and 1.00% (w/v) salinity) to 56.4%. Further investigation of the kinetics of diesel reduction by strain AQ5-05 revealed that the Teissier model had the lowest RMSE and AICC values. The calculated values for the Teissier constants of maximal growth rate, half-saturation rate constant for the maximal growth, and half inhibition constants (μmax, Ks, and Ki), were 0.999 h−1, 1.971% (v/v) and 1.764% (v/v), respectively. The data obtained therefore confirmed the potential application of this cold-tolerant strain in the bioremediation of diesel-contaminated Antarctic soils at low temperature

Medicinal potentials of Strobilanthes crispus (l.) and Orthosiphon stamineus benth. in the management of kidney stones: a review and bibliometric analysis

Introduction In Malaysia, the consumption of tea made from the leaves of Strobilanthes crispus, Orthosiphon stamineus, and their combination is believed by the local people to alleviate kidney stone disease. Therefore, this review was conducted to validate the traditional claims based on the scientific evidences of kidney stones remedies using S crispus and O stamineus. The scientific progress that has evolved over a period of time will be examined using bibliometric analysis. Methodology The data for S crispus and O stamineus related to kidney stones were searched using the Scopus database. A total of 59 publications from 2009 to 2022 were retrieved and analysed using visualisation of similarities viewer software based on the keywords, authors, countries, institutions, and journals. The World Flora Online was used to confirm the identity of the plant species. Results The publications related to O stamineus (50) were found to be higher than S crispus (9). ‘Strobilanthes crispus, Orthosiphon stamineus, and diuretic’ were identified as the most frequently mentioned keywords. Ahmad, M. and Malaysia were the most productive author and country, respectively. Whereas Université de Metz in France and Universiti Putra Malaysia were identified as the most prominent institutions. A number of isolated compounds, including rosmarinic acid and sinensetin, were identified as diuretic agents. While eupatorine and 3′-hydroxy-5,6,7,4′-tetramethoxyflavone were discovered to prevent the formation of calcium oxalate crystals. Conclusions This study offers fresh insights into S crispus and O stamineus plants as a herbal combination for future studies in the treatment of kidney stones

Growth optimisation and kinetic profiling of diesel biodegradation by a cold‒adapted microbial consortium isolated from Trinity Peninsula, Antarctica

Pollution associated with petrogenic hydrocarbons is increasing in Antarctica due to a combination of increasing human activity and the continent’s unforgiving environmental conditions. The current study focuses on the ability of a cold-adapted crude microbial consortium (BS24), isolated from soil on the north-west Antarctic Peninsula, to metabolise diesel fuel as the sole carbon source in a shake-flask setting. Factors expected to influence the efficiency of diesel biodegradation, namely temperature, initial diesel concentration, nitrogen source type and concentration, salinity and pH were studied. Consortium BS24 displayed optimal cell growth and diesel degradation activity at 1.0% NaCl, pH 7.5, 0.5 g/L NH4Cl and 2.0% v/v initial diesel concentration during one-factor-at-a-time (OFAT) analyses. The consortium was psychrotolerant based on the optimum growth temperature of 10‒15 °C. In conventionally optimised media, the highest total petroleum hydrocarbons (TPH) mineralisation was 85% over a 7-day incubation. Further optimisation of conditions predicted through statistical response-surface methodology (RSM) (1.0% NaCl, pH 7.25, 0.75 g/L NH4Cl, 12.5 °C and 1.75% v/v initial diesel concentration) boosted mineralisation to 95% over a 7-day incubation. A Tessier secondary model best described the growth pattern of BS24 in diesel-enriched medium, with maximum specific growth rate, μmax, substrate inhibition constant, Ki and half saturation constant, Ks, being 0.9996 h−1, 1.356% v/v and 1.238% v/v, respectively. The data obtained suggest the potential of microbial consortia such as BS24 in bioremediation applications in low-temperature diesel-polluted soils

Metabolic pathway of phenol of a cold-adapted Antarctic bacterium revealed through whole genome sequencing

Phenol is an important pollutant widely discharged as a component of hydrocarbon fuels, but its degradation in cold regions is challenging due to the harsh environmental conditions. To date, there is little information available concerning the capability for phenol biodegradation by indigenous Antarctic bacteria. In this study, enzyme activities and genes encoding phenol degradative enzymes identified using whole genome sequencing (WGS) were investigated to determine the pathway(s) of phenol degradation of Arthrobacter sp. strains AQ5-05 and AQ5-06, originally isolated from Antarctica. Complete phenol degradative genes involved only in the ortho-cleavage were detected in both strains. This was validated using assays of the enzymes catechol 1,2-dioxygenase and catechol 2,3-dioxygenase, which indicated the activity of only catechol 1,2-dioxygenase in both strains, in agreement with the results from the WGS. Both strains were psychrotolerant with the optimum temperature for phenol degradation, being between 10 and 15 °C. This study suggests the potential use of cold-adapted bacteria in the bioremediation of phenol pollution in cold environments

Statistical optimisation of diesel biodegradation at low temperatures by an Antarctic marine bacterial consortium isolated from non-contaminated seawater

Hydrocarbon pollution is widespread around the globe and, even in the remoteness of Antarctica, the impacts of hydrocarbons from anthropogenic sources are still apparent. Antarctica’s chronically cold temperatures and other extreme environmental conditions reduce the rates of biological processes, including the biodegradation of pollutants. However, the native Antarctic microbial diversity provides a reservoir of cold-adapted microorganisms, some of which have the potential for biodegradation. This study evaluated the diesel hydrocarbon-degrading ability of a psychrotolerant marine bacterial consortium obtained from the coast of the north-west Antarctic Peninsula. The consortium’s growth conditions were optimised using one-factor-at-a-time (OFAT) and statistical response surface methodology (RSM), which identified optimal growth conditions of pH 8.0, 10 °C, 25 ppt NaCl and 1.5 g/L NH4NO3. The predicted model was highly significant and confirmed that the parameters’ salinity, temperature, nitrogen concentration and initial diesel concentration significantly influenced diesel biodegradation. Using the optimised values generated by RSM, a mass reduction of 12.23 mg/mL from the initial 30.518 mg/mL (4% (w/v)) concentration of diesel was achieved within a 6 d incubation period. This study provides further evidence for the presence of native hydrocarbon-degrading bacteria in non-contaminated Antarctic seawater

​​The utilisation of Antarctic microalgae isolated from Paradise Bay (Antarctic Peninsula) in the bioremediation of diesel

Research has confirmed that the utilisation of Antarctic microorganisms, such as bacteria, yeasts and fungi, in the bioremediation of diesel may provide practical alternative approaches. However, to date there has been very little attention towards Antarctic microalgae as potential hydrocarbon degraders. Therefore, this study focused on the utilisation of an Antarctic microalga in the bioremediation of diesel. The studied microalgal strain was originally obtained from a freshwater ecosystem in Paradise Bay, western Antarctic Peninsula. When analysed in systems with and without aeration, this microalgal strain achieved a higher growth rate under aeration. To maintain the growth of this microalga optimally, a conventional one-factor-at a-time (OFAT) analysis was also conducted. Based on the optimized parameters, algal growth and diesel degradation performance was highest at pH 7.5 with 0.5 mg/L NaCl concentration and 0.5 g/L of NaNO3 as a nitrogen source. This currently unidentified microalga flourished in the presence of diesel, with maximum algal cell numbers on day 7 of incubation in the presence of 1% v/v diesel. Chlorophyll a, b and carotenoid contents of the culture were greatest on day 9 of incubation. The diesel degradation achieved was 64.5% of the original concentration after 9 days. Gas chromatography analysis showed the complete mineralisation of C7–C13 hydrocarbon chains. Fourier transform infrared spectroscopy analysis confirmed that strain WCY_AQ5_3 fully degraded the hydrocarbon with bioabsorption of the products. Morphological and molecular analyses suggested that this spherical, single-celled green microalga was a member of the genus Micractinium. The data obtained confirm that this microalga is a suitable candidate for further research into the degradation of diesel in Antarctica

Statistical optimisation of phenol degradation and pathway identification through whole genome sequencing of the cold-adapted Antarctic bacterium, Rhodococcus sp. strain AQ5-07

Study of the potential of Antarctic microorganisms for use in bioremediation is of increasing interest due to their adaptations to harsh environmental conditions and their metabolic potential in removing a wide variety of organic pollutants at low temperature. In this study, the psychrotolerant bacterium Rhodococcus sp. strain AQ5-07, originally isolated from soil from King George Island (South Shetland Islands, maritime Antarctic), was found to be capable of utilizing phenol as sole carbon and energy source. The bacterium achieved 92.91% degradation of 0.5 g/L phenol under conditions predicted by response surface methodology (RSM) within 84 h at 14.8 °C, pH 7.05, and 0.41 g/L ammonium sulphate. The assembled draft genome sequence (6.75 Mbp) of strain AQ5-07 was obtained through whole genome sequencing (WGS) using the Illumina Hiseq platform. The genome analysis identified a complete gene cluster containing catA, catB, catC, catR, pheR, pheA2, and pheA1. The genome harbours the complete enzyme systems required for phenol and catechol degradation while suggesting phenol degradation occurs via the β-ketoadipate pathway. Enzymatic assay using cell-free crude extract revealed catechol 1,2-dioxygenase activity while no catechol 2,3-dioxygenase activity was detected, supporting this suggestion. The genomic sequence data provide information on gene candidates responsible for phenol and catechol degradation by indigenous Antarctic bacteria and contribute to knowledge of microbial aromatic metabolism and genetic biodiversity in Antarctica

Statistical Optimisation of Diesel Biodegradation at Low Temperatures by an Antarctic Marine Bacterial Consortium Isolated from Non-Contaminated Seawater

Hydrocarbon pollution is widespread around the globe and, even in the remoteness of Antarctica, the impacts of hydrocarbons from anthropogenic sources are still apparent. Antarctica’s chronically cold temperatures and other extreme environmental conditions reduce the rates of biological processes, including the biodegradation of pollutants. However, the native Antarctic microbial diversity provides a reservoir of cold-adapted microorganisms, some of which have the potential for biodegradation. This study evaluated the diesel hydrocarbon-degrading ability of a psychrotolerant marine bacterial consortium obtained from the coast of the north-west Antarctic Peninsula. The consortium’s growth conditions were optimised using one-factor-at-a-time (OFAT) and statistical response surface methodology (RSM), which identified optimal growth conditions of pH 8.0, 10 °C, 25 ppt NaCl and 1.5 g/L NH4NO3. The predicted model was highly significant and confirmed that the parameters’ salinity, temperature, nitrogen concentration and initial diesel concentration significantly influenced diesel biodegradation. Using the optimised values generated by RSM, a mass reduction of 12.23 mg/mL from the initial 30.518 mg/mL (4% (w/v)) concentration of diesel was achieved within a 6 d incubation period. This study provides further evidence for the presence of native hydrocarbon-degrading bacteria in non-contaminated Antarctic seawater