Non-conventional Carbon Sources Research Articles

System metabolic engineering of Escherichia coli W for the production of 2-ketoisovalerate using unconventional feedstock.

Replacing traditional substrates in industrial bioprocesses to advance the sustainable production of chemicals is an urgent need in the context of the circular economy. However, since the limited degradability of non-conventional carbon sources often returns lower yields, effective exploitation of such substrates requires a multi-layer optimization which includes not only the provision of a suitable feedstock but the use of highly robust and metabolically versatile microbial biocatalysts. We tackled this challenge by means of systems metabolic engineering and validated Escherichia coli W as a promising cell factory for the production of the key building block chemical 2-ketoisovalerate (2-KIV) using whey as carbon source, a widely available and low-cost agro-industrial waste. First, we assessed the growth performance of Escherichia coli W on mono and disaccharides and demonstrated that using whey as carbon source enhances it significantly. Second, we searched the available literature and used metabolic modeling approaches to scrutinize the metabolic space of E. coli and explore its potential for overproduction of 2-KIV identifying as basic strategies the block of pyruvate depletion and the modulation of NAD/NADP ratio. We then used our model predictions to construct a suitable microbial chassis capable of overproducing 2-KIV with minimal genetic perturbations, i.e., deleting the pyruvate dehydrogenase and malate dehydrogenase. Finally, we used modular cloning to construct a synthetic 2-KIV pathway that was not sensitive to negative feedback, which effectively resulted in a rerouting of pyruvate towards 2-KIV. The resulting strain shows titers of up to 3.22 ± 0.07g/L of 2-KIV and 1.40 ± 0.04g/L of L-valine in 24h using whey in batch cultures. Additionally, we obtained yields of up to 0.81g 2-KIV/g substrate. The optimal microbial chassis we present here has minimal genetic modifications and is free of nutritional autotrophies to deliver high 2-KIV production rates using whey as a non-conventional substrate.

Biosurfactant Production from Pineapple Waste and Application of Experimental Design and Statistical Analysis.

The use of non-conventional carbon sources for biosurfactant-producing microorganisms is a promising alternative in fermentation to substitute costly substrates. So, the current research used pineapple peel as a cost-effective and renewable substrate because of its rich composition in minerals and sugars and high availability. Following a 22 full factorial design, a bacterial strain of Bacillus subtilis produced biosurfactants in fermentative media containing different concentrations of glucose and concentrated pineapple peel juice (CPPJ). The influence of these two independent variables was evaluated according to three different responses: surface tension reduction rate (STRR), emulsification index (EI24), and concentration of semi-purified biosurfactant (SPB). The maximum value for STRR (57.63%) was obtained in media containing 0.58% glucose (w/v) and 5.82% CPPJ (v/v), while the highest EI24 response (58.60%) was observed at 2% glucose (w/v) and 20%CPPJ(v/v) and maximum SPB (1.28g/L) at 3.42% glucose(w/v) and 34.18% CPPJ(v/v). Statistical analysis indicated that the CPPJ variable mostly influenced the STRR and SPB responses, whereas the EI24 was significantly influenced by pineapple peel juice and glucose contents.

Ni and Cu recovery by bioleaching from the printed circuit boards of mobile phones in non-conventional medium

There is a substantial volume of mobile phone waste every year. Due to the disadvantages of traditional methods, it is necessary to look for biological processes that are more eco-friendly and economical to recover metals from e-waste. Fungi provide large amounts of organic acids and dissolve metals but using sucrose in the medium is not economical. In this paper, the main objective is to find a suitable alternative carbon substrate instead of sucrose for fungi bioleaching of Ni and Cu in printed circuit boards (PCBs) of mobile phones using Penicillium simplicissimum. Four kinds of carbon sources (including sucrose, cheese whey, sugar, and sugar cane molasses) were selected. Also, pH and number of spores in inoculum were optimized by response surface methodology (RSM) for all carbon sources. The results showed the simultaneous maximum recovery of Cu and Ni is not possible. For Cu recovery, sugar is the best economical and simplistic medium instead of sucrose. Maximum recovery of Cu (90%) gained at the pH of 7, 3.3 × 107 spores, and in sugar. The amount of Ni recovery (89%) was highest in molasses, at the pH of 2, and 106 spores. The results proved non-conventional carbon sources improve bioleaching efficiency and the possibility of industrialization.

Macroalgal biomass subcritical hydrolysates for the production of polyhydroxyalkanoate (PHA) by Haloferax mediterranei

Non-conventional carbon sources, such as macroalgae, are sustainable alternatives for large-scale production of biopolymers. The present study examined macroalgae-derived carbohydrates, as carbon sources for the production of polyhydroxyalkanoates (PHAs) by Haloferax mediterranei. Simulants of the hydrolysates of seven different macroalgal biomasses were prepared and the PHA production was studied. A maximum biomass concentration with maximum PHA content was detected in medium prepared from green macroalgae. The highest cell dry weight and PHA concentrations were 3.8 ± 0.2 g·L−1 and 2.2 ± 0.12 g·L−1 respectively when Haloferax mediterranei was grown in 25% (w/w) of Ulva sp. hydrolysate, at 42 °C temperature and initial pH of 7.2. Poly(3-hydroxy-butyrate-co-3-hydroxyvalerate was the major PHA constituent. The present study demonstrated that Ulva sp. is a promising feedstock for PHA production.

Production of biopolyester poly(3-hydroxybutyrate) by Bacillus cereus RCL 02, a leaf endophyte of Ricinus communis L.

Endophytic bacteria colonizing the internal tissues of plants have attracted the attention of scientific communities in recent years for production of biodegradable polyesters like polyhydroxyalkanotaes (PHAs). A newly characterized bacterium, Bacillus cereus RCL 02 (GenBank accession no. KX458035), isolated from surface sterilized leaves of Ricinus communis L. has been explored for the production of poly(3-hydroxybutyrate) [P(3HB)], the most common PHA. As revealed by scanning electron microscopy, P(3HB) accumulating cells developed swellings or blebs and released the native granules as a function of autolysis. During growth in glucose containing mineral salts medium under batch fermentation, the isolate produced P(3HB) accounting 68% of its cell dry weight (CDW). Glucose and yeast extract when used in the ratio of 5:1, significantly influenced intracellular biopolyester accumulation (72.2%, CDW and 2.54 g/L). A further increase of polymer production (81%, CDW and 3.17 g/L) was accomplished in presence of 1.5 mM manganese as exogenous metal stress. Moreover, supplementation of the growth medium with non-conventional carbon sources especially refined sugarcane molasses further enhanced the production of both biomass (9.44 g/L) as well as polyester (83.6%, CDW and 7.89 g/L). These finding emphasises exploration of endophytic bacteria of oleaginous plants in general and R. communis L. in particular as potential but hitherto an under exploited bioresource for commercial production of biodegradable polyesters.

Modulation of fatty acid metabolism and tricarboxylic acid cycle to enhance the lipstatin production through medium engineering in Streptomyces toxytricini

This work investigated the potential of medium engineering to obtain maximum biomass, non-conventional carbon sources for lipstatin production and modulation of tricarboxylic acid (TCA) cycle to promote lipstatin synthesis. It was found that 2:3 carbon and nitrogen ratio, produced maximum biomass of 7.9g/L in growth medium and 6.6g/L in pre-seed medium. Among the studied non-conventional carbon sources i.e., soya flour 40g/L and sesame oil 30mL/L were found producing 1109.37mg/L (1.24-fold of control) and 1196.75mg/L (1.34-fold of control) lipstatin respectively. Supplementation of TCA cycle intermediates revealed that NADH and succinic acid showed lipstatin production to 1132.99mg/L and 1171.10mg/L respectively. Experimental outcome was validated in 7L bioreactor and produced 2242.63mg/L lipstatin which was ∼14% higher than shake flask.

Influence of growth conditions on production of poly(3-hydroxybutyrate) by Bacillus cereus HAL 03 endophytic to Helianthus annuus L.

Bioconversion of sugarcane molasses to poly(3-hydroxybutyrate-co-3- hydroxyvalerate) by endophytic Bacillus cereus RCL 02Rituparna Das, Arundhati Pal, Amal Kanti Paul

EFFECT OF NON-CONVENTIONAL CARBON SOURCES ON THE PRODUCTION OF TRITERPENOIDS IN SUBMERGED CULTURES OF Pleurotus MACROFUNGI

Among the secondary metabolites of pharmacological, chemical and biotechnological interest, triterpenoidal compounds are widely distributed throughout the fungi kingdom. Triterpenoids produced by species of the genus Pleurotus, basidiomycetes characterized by their important biological actions and excellent nutritional quality, can be obtained by fermentation processes that stimulate the production of the bioactive compounds. This study evaluates the effect of using 12 non-conventional carbon sources (CS) on the production of triterpenoids from 3 Pleurotus species: P. ostreatus, P. djamor and P. pulmonarius obtained in submerged culture. The variations found among these species with regard to their quantities and structural differences were dependent on the CS as well as the species, and it was concluded that the cultivation of the mycelium of P. pulmonarius with wheat bran promotes the production of the compounds of interest. In addition no direct influence of the C/N ratio of the substrate on the biosynthesis of the triterpenoids was observed, as reported in the case of other secondary metabolites such as polysaccharides and statins.

Production of Biomass, Polysaccharides, and Ganoderic Acid using Non-conventional Carbon Sources under Submerged Culture of the Lingzhi or Reishi Medicinal Mushroom, Ganoderma lucidum (W.Curt.:Fr.)P. Karst. (Higher Basidiomycetes)

The effect of different non-conventional carbon sources was studied in the submerged culture of Lingzhi or Reishi medicinal mushroom, Ganoderma lucidum, for simultaneous production of mycelial biomass, bioactive ganoderic acid, and polysaccharides, in less time, using non-conventional carbon sources to minimize the high costs of current culture media. The optimal medium composition was defined as (g/L): 50 of barley flour, 0.2 of KH2PO4, 0.1 of MgSO4ⁱ7H2O, and 1 NH4Cl. Cultivated under this complex culture medium, the mycelial biomass production was 23.49 ± 0.37 g/L; the extracellular polysaccharides production was 2.72 ± 0.11 g/L; the intracellular polysaccharides production was 2.22 ± 0.06 g/L; the ganoderic acids production was 299.67 ± 11.63 mg/L. One liter of culture medium developed in this project was priced at USD $ 0.11 if barley flour is used as carbon source or $ 0.13 with oat flour in order to get a good amount of products of interest.

Trichosporon wieringae sp.nov., an anamorphic basidiomycetous yeast from soil, and assimilation of some phenolic compounds, polysaccharides and other non-conventional carbon sources by saprophytic Trichosporon species

Trichosporon wieringae sp.nov., an anamorphic basidiomycetous yeast from soil, and assimilation of some phenolic compounds, polysaccharides and other non-conventional carbon sources by saprophytic Trichosporon species

Trichosporon wieringae sp.nov., an anamorphic basidiomycetous yeast from soil, and assimilation of some phenolic compounds, polysaccharides and other non-conventional carbon sources by saprophytic Trichosporon species

A morphological and physiological description of an anamorphic basidiomycetous yeast species isolated from soil, named Trichosporon wieringae, is presented. The phylogenetic position within the genus, based on nuclear base sequencing of the D1/D2 region of the large subunit of rDNA and of the ITS region reveals close relationship to the Porosum clade of the genus Trichosporon Behrend, T. gamsii being the closest relative. The ability of non-pathogenic Trichosporon species to assimilate uric acid, ethylamine, l-4-hydroxyproline, some aromatic compounds and polysaccharides as sole sources of carbon and energy was studied. An identification key to these species, based on growth tests on these non-conventional carbon sources, is proposed. The type strain of T. wieringae is CBS 8903 (JCM 12201).

A novel promoter, derived from the isocitrate lyase gene of Candida tropicalis, inducible with acetate in Saccharomyces cerevisiae

When the isocitrate lyase gene, containing 5'-upstream and 3'-flanking regions, of an n-alkane-assimilating yeast Candida tropicalis was introduced into Saccharomyces cerevisiae, the enzyme was functionally overexpressed in the cells grown on acetate. The amount of the recombinant isocitrate lyase expressed in S. cerevisiae was as much as 30% of the total soluble proteins in the cells, being comparable to that with GAL7 functional under the control of galactose. The expression was also observed when the cells were grown on glycerol, lactate, ethanol or oleate. These facts indicate that the isocitrate lyase gene upstream region (UPR-ICL) contains a strong promoter functional in S. cerevisiae. UPR-ICL is active as a promoter on cheap carbon sources such as acetate and nonconventional carbon sources such as oleate, whereas many conventional strong promoters demand relatively expensive sugars or sugar derivatives. Therefore, it is promising to construct an economical recombinant protein production system by using UPR-ICL.