Yusuf Y. Deeni

Fermentation of stalk juices from different Nigerian sorghum cultivars to ethanol

Abstract For improved production of ethanol from sorghum stalk juice fermentation, cultivation location and cultivar type are important factors to consider. In the present study, SSV2 and KSV8 sorghum cultivars were cultivated in Kano and Kaduna states in Nigeria that exhibit notably different rain precipitation and diurnal temperatures. The crude stalk juices (without pre-treatment or nutrient supplementation) were extracted from these sorghum samples and fermented with a distiller’s strain of the yeast, Saccharomyces cerevisiae. Sugar consumption and alcohol production were determined by HPLC and GC-MS, respectively. When it was grown in the Kaduna site, SSV2 was identified as the highest yielding sorghum cultivar from which we extracted the maximum levels of extractable sugars (161.50 g l-1 ) that yielded favourable ethanol levels of 80.56 g l-1 following fermentation. Our findings show that relatively colder and wetter cultivation sites are preferred for sorghum stalk juice destined for bioethanol production

NRF2 Regulates HER2 and HER3 Signaling Pathway to Modulate Sensitivity to Targeted Immunotherapies

NF-E2 related factor-2 (NRF2) is an essential transcription factor for multiple genes encoding antioxidants and detoxification enzymes. NRF2 is implicated in promoting cancer therapeutic resistance by its detoxification function and crosstalk with proproliferative pathways. However, the exact mechanism of this intricate connectivity between NRF2 and growth factor induced proliferative pathway remains elusive. Here, we have demonstrated that pharmacological activation of NRF2 by tert-butylhydroquinone (tBHQ) upregulates the HER family receptors, HER2 and HER3 expression, elevates pAKT levels, and enhances the proliferation of ovarian cancer cells. Preactivation of NRF2 also attenuates the combined growth inhibitory effects of HER2 targeting monoclonal antibodies, Pertuzumab and Trastuzumab. Further, tBHQ caused transcriptional induction of HER2 and HER3, while SiRNA-mediated knockdown of NRF2 prevented this and further caused transcriptional repression and enhanced cytotoxicity of the HER2 inhibitors. Hence, NRF2 regulates both HER2 and HER3 receptors to influence cellular responses to HER2 targeting monoclonal antibodies. This deciphered crosstalk mechanism reinforces the role of NRF2 in drug resistance and as a relevant anticancer target.

Predicting the minimum liquid surface tension activity of pseudomonads expressing biosurfactants

Bacteria produce a variety of biosurfactants capable of significantly reducing liquid (aqueous) surface tension (γ) with a range of biological roles and biotechnological uses. To determine the lowest achievable surface tension (γMin), we tested a diverse collection of Pseudomonas‐like isolates from contaminated soil and activated sludge and identified those expressing biosurfactants by drop‐collapse assay. Liquid surface tension‐reducing ability was quantitatively determined by tensiometry, with 57 isolates found to significantly lower culture supernatant surface tensions to 24·5–49·1 mN m−1. Differences in biosurfactant behaviour determined by foaming, emulsion and oil‐displacement assays were also observed amongst isolates producing surface tensions of 25–27 mN m−1, suggesting that a range of structurally diverse biosurfactants were being expressed. Individual distribution identification (IDI) analysis was used to identify the theoretical probability distribution that best fitted the surface tension data, which predicted a γMin of 24·24 mN m−1. This was in agreement with predictions based on earlier work of published mixed bacterial spp. data, suggesting a fundamental limit to the ability of bacterial biosurfactants to reduce surface tensions in aqueous systems. This implies a biological restriction on the synthesis and export of these agents or a physical–chemical restriction on their functioning once produced.

Uncovering behavioural diversity amongst high-strength Pseudomonas spp. surfactants at the limit of liquid surface tension reduction

&NA; Bacterial biosurfactants have a wide range of biological functions and biotechnological applications. Previous analyses had suggested a limit to their reduction of aqueous liquid surface tensions (&ggr;Min), and here we confirm this in an analysis of 25 Pseudomonas spp. strains isolated from soil which produce high‐strength surfactants that reduce surface tensions to 25.2 ± 0.1‐26.5 ± 0.2 mN m‐1 (the surface tension of sterile growth medium and pure water was 52.9 ± 0.4 mN m‐1 and 72.1 ± 1.2 mN m‐1, respectively). Comparisons of culture supernatants produced using different growth media and semi‐purified samples indicate that the limit of 24.2‐24.7 mN m‐1 is not greatly influenced by culture conditions, pH or NaCl concentrations. We have used foam, emulsion and oil‐displacement behavioural assays as a simple and cost‐effective proxy for in‐depth biochemical characterisation, and these suggest that there is significant structural diversity amongst these surfactants that may reflect different biological functions and offer new biotechnological opportunities. Finally, we obtained a draft genome for the strain producing the highest strength surfactant, and identified a cluster of non‐ribosomal protein synthase genes that may produce a cyclic lipopeptide (CLP)‐like surfactant. Further investigation of this group of related bacteria recovered from the same site will allow a better understanding of the significance of the great variety of surfactants produced by bacterial communities found in soil and elsewhere. &NA; Graphical Abstract Figure. Bacterial biosurfactants appear to have a limit to aqueous liquid surface tension activity of ˜24 mN m‐1, which is approached by a number of pseudomonad surfactants showing significant behavioural diversity.

Biofilm formation and cellulose expression by Bordetella avium 197N, the causative agent of bordetellosis in birds and an opportunistic respiratory pathogen in humans

Although bacterial cellulose synthase (bcs) operons are widespread within the Proteobacteria phylum, subunits required for the partial-acetylation of the polymer appear to be restricted to a few γ-group soil, plant-associated and phytopathogenic pseudomonads, including Pseudomonas fluorescens SBW25 and several Pseudomonas syringae pathovars. However, a bcs operon with acetylation subunits has also been annotated in the unrelated β-group respiratory pathogen, Bordetella avium 197N. Our comparison of subunit protein sequences and GC content analyses confirms the close similarity between the B. avium 197N and pseudomonad operons and suggests that, in both cases, the cellulose synthase and acetylation subunits were acquired as a single unit. Using static liquid microcosms, we can confirm that B. avium 197N expresses low levels of cellulose in air-liquid interface biofilms and that biofilm strength and attachment levels could be increased by elevating c-di-GMP levels like the pseudomonads, but cellulose was not required for biofilm formation itself. The finding that B. avium 197N is capable of producing cellulose from a highly-conserved, but relatively uncommon bcs operon raises the question of what functional role this modified polymer plays during the infection of the upper respiratory tract or survival between hosts, and what environmental signals control its production.

Bioconversion of degraded husked sorghum grains to ethanol

Abstract Efficient starch saccharification is an essential step towards achieving improved ethanol yields by fermentation. Sorghum grains are important starch sources for bioconversion to ethanol. In the present study, disease degraded (spoilt) husked grains from Nigerian sorghum cultivars were obtained from field sites and subjected to bioprocessing to ethanol. The crude husked grains (comprising husks, spikelet, awn, rachis and pubescence materials) were hammer milled and each meal separately mashed with enzyme cocktails comprising amylase, glucanase and protease enzymes. The saccharified worts obtained were then fermented with the yeasts, Saccharomyces cerevisiae and Pichia stipitis (aka Scheffersomyces stipitis), without exogenous nutrient supplementation. Sugars liberated during mashing were determined and it was found that enzymatic hydrolysis of milled sorghum grains was effective in yielding favourable levels of fermentable sugars up to 70g sugar/100g substrate with one particular cultivar (KSV8). Ethanol and carbon dioxide production was measured from subsequent trial fermentations of the sorghum mash and it was found that S. cerevisiae produced ethanol levels equating to 420 L/t that compares very favourably with yields from wheat and barley. Our findings show that crude degraded sorghum grains represent favourable low-cost feedstocks for bioconversion to ethanol with reduced energy input and without additional costs for nutrient supplementation during fermentation. Consequently, our results suggest some economic benefits could be derived from spoilt or degraded sorghum grains.

NRF2 Regulates HER1 Signaling Pathway to Modulate the Sensitivity of Ovarian Cancer Cells to Lapatinib and Erlotinib

NF-E2-related factor 2 (NRF2) regulates the transcription of a battery of metabolic and cytoprotective genes. NRF2 and epidermal growth factor receptors (EGFRs/HERs) are regulators of cellular proliferation and determinants of cancer initiation and progression. NRF2 and HERs confer cancers with resistance to several therapeutic agents. Nevertheless, there is limited understanding of the regulation of HER expression and activation and the link between NRF2 and HER signalling pathways. We show that NRF2 regulates both basal and inducible expression of HER1, as treatment of ovarian cancer cells (PEO1, OVCAR3, and SKOV3) with NRF2 activator tBHQ inducing HER1, while inhibition of NRF2 by siRNA knockdown or with retinoid represses HER1. Furthermore, treatment of cells with tBHQ increased total and phosphorylated NRF2, HER1, and AKT levels and compromised the cytotoxic effect of lapatinib or erlotinib. Treatment with siRNA or retinoid antagonised the effect of tBHQ on NRF2 and HER1 levels and enhanced the sensitivity of ovarian cancer cells to lapatinib or erlotinib. Pharmacological or genetic inhibition of NRF2 and/or treatment with lapatinib or erlotinib elevated cellular ROS and depleted glutathione. This extends the understanding of NRF2 and its regulation of HER family receptors and opens a strategic target for improving cancer therapy.