vanillin

The widespread use of vanillin in food and pharmaceutical industries increases the probability of entering to the waters and its positive or negative effects on growth and life of aquatic algae. Due to the nutritional and medical importance of Spirulina platensis, a blue-green micro-alga, the effect of vanillin on its growth and physiological characteristics was considered in two Zarrouk and Johnson media, on 0, 21, 27 and 33 days of a 42 days period. The highest dry weight was obtained in Zarrouk and then Zarrouk containing vanillin media, whilst the highest growth was observed in Zarrouk and then Johnson media. A positive and strong correlation (R 2=0.94, p<0.01) was observed between the turbidity of suspension at 560 nm with its dry weight. Vanillin reduced growth and dry biomass in all days of sampling, but in contrast increased the amount of lipid and protein in both media. The amounts of chlorophyll a, carotenoids, phycocyanin, allophycocyanin, phycoerythrin, astaxanthin, phenol, carbohydrate and lipid peroxidation were often higher in Johnson medium (without vanillin). Although, the recent medium in most cases induced the maximum cell productions, but Zarrouk medium, compared to the Zarrouk containing vanillin medium, showed some inverse results. In general, although vanillin led to a reduction in algal growth and biomass, but in cases where valuable products such as antioxidants, pigments, lipid compounds, protein, carbohydrates and phenols are considered, it can be used as an inducing factor of production.

One of the important goals of plant physiology in water ecosystems, is biomass and growth increment of green microalgae which led to access to their valuable production. In this regard, many factors are able to influence the increment and decrement of algal biomass. In this research different levels of vanillin (C8H8O3), as 0 (control), 10, 25, 40, 50, 70, 90 and 100 mg. L-1, were investigated during 24 days on cell number, fresh weight, dry weight and some of physiological indices (such as total sugar, reducing sugars, protein and photosynthetic pigments) in two algae, D. badawil-UTEX2538 and D. salina-UTEX200. All experiments were performed as completely randomized design (CRD) in three replications. The highest number of cells was observed at 25, 40 and 50 mg. L-1 vanillin treatments. In D. bardawil, maximum specific growth rate (SGR) and minimum doubling time (DT) of cells were observed at 50 mg. L-1 and in D. salina those were observed at 25 and 40 mg. L-1. Fresh weight, dry weight and total sugar were increased by the most of treatments, but protein and reducing sugars were decreased compared to control. Chl a, total Chl and total carotenoid were increased only in D. bardawil, but Chl b and beta carotene showed decrements. D. salina had a higher growth rate but lower content of protein, total sugar and reducing sugars than D. bardawil. Overall, in contrast to some of the previous researches, vanillin which has phenolic nature induced faster growth rate and cell division in algal suspensions and also in the most of the cases, it led to improvement of physiological indices.

In the recent years, the use of microbial biotransformation processes to achieve specific properties of vanillin and access to the natural vanillin origin has been a lot of attention. In the present study, Taguchi method was employed for optimizing the biotransformation of isoeugenol to vanillin under resting cells of native isolate Psychrobacter sp. strain CSW4. Five factors, i.e. initial isoeugenol concentration, initial dry biomass, co-substrates (glycerol, yeast extract and tryptone), initial NaCl concentration and metal ions (Cu, Zn and Co, were selected and experiments based on an orthogonal array layout of L18 were performed. Vanillin produced in the biotransformation reaction mixture was analyzed by HPLC method. Optimization of the process by Taguchi method showed that highest impact factors with importance priority of NaCl concentration, initial isoeugenol concentration, glycerol as substrate, cobalt ion and initial dry biomass were determined as optimum conditions for the biotransformation isoeugenol into vanillin, respectively. Under these optimized conditions, the highest vanillin concentration (1.016 g/L) obtained after 24-h reaction biotransformation. The molar yield of vanillin produced from isoeugenol was 43.8%. Results of this study indicate that if optimization of medium composition is performed to balance the cell growth and vanillin amount, reasonable yields of vanillin have been achieved, without addition ofany toxic organic solvent or other chemicals which increase the cost of production.