Abstract
Various chemicals, i.e., furfural, vanillin, 4-hydroxybenzaldehyde and acetate produced during the pretreatment of biomass affect microbial fermentation. In this study, effect of vanillin, 4-hydroxybenzaldehyde and acetate on antibiotic production in Streptomyces coelicolor is investigated. IC 50 value of vanillin, 4-hydroxybenzaldehyde and acetate was recorded as 5, 11.3 and 115 mM, respectively. Vanillin was found as a very effective molecule, and it completely abolished antibiotic (undecylprodigiosin and actinorhodin) production at 1 mM concentration, while 4-hydroxybenzaldehyde and acetate have little effect. Microscopic analysis with field emission scanning electron microscopy (FESEM) showed that addition of vanillin inhibits mycelia formation and increases differentiation of S. coelicolor cells. Vanillin increases expression of genes responsible for sporulation (ssgA) and decreases expression of antibiotic transcriptional regulator (redD and actII-orf4), while it has no effect on genes related to the mycelia formation (bldA and bldN) and quorum sensing (scbA and scbR). Vanillin does not affect the glycolysis process, but may affect acetate and pyruvate accumulation which leads to increase in fatty acid accumulation. The production of antibiotics using biomass hydrolysates can be quite complex due to the presence of exogenous chemicals such as furfural and vanillin, and needs further detailed study.Electronic supplementary materialThe online version of this article (doi:10.1007/s13205-016-0539-y) contains supplementary material, which is available to authorized users.
Highlights
Lignocellulose is a complex-structured biomass composed of cellulose, hemicelluloses, and lignin
Lignocellulose pretreatment using different methods lead to the release of different inhibitors, i.e., furfural, vanillin, 4-hydroxybenzaldehyde, and acetate, which further affects the ability of microbes to utilize free sugar as a carbon source (Allen et al 2010)
Most of the research groups have reported that biomass-derived molecules act as an inhibitor, but interestingly in our previous research we found that furfural can elicit antibiotic production in S. coelicolor and it can be used to increase undecylprodigiosin production (Bhatia et al 2016)
Summary
Lignocellulose is a complex-structured biomass composed of cellulose, hemicelluloses, and lignin It cannot be used as carbon source directly and it should be available as fermentable sugar (Bhatia et al 2015a, 2016; Verma et al 2016). Lignocellulose pretreatment using different methods lead to the release of different inhibitors, i.e., furfural, vanillin, 4-hydroxybenzaldehyde, and acetate, which further affects the ability of microbes to utilize free sugar as a carbon source (Allen et al 2010). Regulation is influenced by various low molecular mass compounds, transfer RNA, sigma factors and gene products formed during post-exponential development. These events generate signals which affect a cascade of regulatory events resulting in chemical differentiation (secondary metabolism) and morphological differentiation (morphogenesis). Effect of other inhibitory molecules (vanillin, 4-hydroxybenzaldehyde and acetate) on antibiotic production and expression of various regulatory genes were studied
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