Optimization of hazelnut husk medium for pullulan production by a domestic A. pullulans strain.

Hazelnut husk is one of the most abundant agricultural residue in Turkey. Valorization of this lignocellulosic biomass would provide a promoting alternative for economical production of pullulan. In this study, dried hazelnut husk hydrolysate was used directly as fermentation medium for pullulan production by a domestic strain of Aureobasidium pullulans. The aim of this work was the optimization of some fermentation medium parameters by central composite design using response surface methodology (RSM). The effects of (NH4)2SO4 concentration, the volume of concentrated H2SO4 and the amount of ground hazelnut husk on pullulan production were optimized by RSM. The optimum levels of the fermentation parameters defined as 7.2 gL-1, 2.5 mL and 20 g, respectively. The maximum pullulan and exopolysaccharide concentrations were determined as 74.39 and 75.95 gL-1, respectively in the optimum conditions. Specific growth rate of the strain was found as 0.097 h-1. FTIR spectral attributes confirmed the structure of pullulan. Thermal decomposition temperature of synthesized pullulan was found as 247.15 °C. This study showed that hazelnut husk was one of the novel substrate for production of the pullulan by A. pullulans AZ-6. No previous work was found to utilize dried hazelnut husk as fermentation medium for pullulan production by A. pullulans.

Evaluation of Some Agro-Industrial Wastes as Fermentation Medium for Pullulan Production by Aureobasidium pullulans AZ-6.

Agro-industrial wastes are rich sources of some nutrients. Thus, utilization of wastes seems to be ecologically sound and economically advantageous. The aim of this work was to investigate the potential usage of various agro-industrial wastes as fermentation medium for pullulan production by a domestic strain; Aureobasidium pullulans AZ-6. In this study, different agro-industrial wastes; various citrus peels, grape pomace, the hydrolysates of hazelnut and chestnut shells, sugarcane molasses residue, dried and fresh hazelnut husks and pumpkin peel, were used as fermentation media without adding any extra nutritional component for pullulan production by A. pullulans AZ-6. As a result, among the tested media, the maximum pullulan concentration was obtained as 33.59 gL-1 using the sugarcane molasses residue, and followed by the corresponding value of 30.02 gL-1 obtained in the dried hazelnut husk hydrolysate medium. Therefore, the usage of agro-industrial wastes as fermentation media is considered to make pullulan production cost effective. In addition, waste treatment from this aspect solves a relevant environmental problem. In this study, sugarcane molasses residue and dried hazelnut husk hydrolysate were used directly as fermentation media for pullulan production for the first time. Pullulan production from sugarcane molasses residue and dried hazelnut husk hydrolysate media might be a promising substrate for economical point of view.

Yeast Identification During Fermentation of Turkish Gemlik Olives.

Naturally fermented black table olives of the Gemlik variety are one of the most consumed fermented products in Turkey. The objective of this work was to identify yeast strains isolated during their natural fermentation by using Restriction Fragments Lengths Polymorphism-Polimerase Chain Reaction (RFLP-PCR) and DNA sequencing methods. The study also focused on determining the effect of regional differences on yeast microflora of naturally fermented Gemlik olives. A total of 47 yeast strains belonging to 12 different species which had been previously isolated from the natural brine of Akhisar and Iznik-Gemlik cv. olives were characterized by molecular methods. Forty-two of the tested strains could be identified by RFLP-PCR to species level. These yeast species were determined as Candida mycetangi, Candida hellenica, Candida membranaefaciens, Candida famata, Candida pelliculosa, Saccharomyces cerevisiae, and Zygosaccharomyces mrakii. Five strains were identified by DNA sequencing. These strains belonged to three different species: Aureobasidium pullulans, Kloeckera apiculate, and Cryptococcus saitoi. The most frequent species were C. famata and C. pelliculosa in both regions. PRACTICAL APPLICATION: This work studies the yeasts from Turkish table olives which could prove to be of importance to the food industry in that area. On the other hand, it compares identification by molecular and classical biochemical methods and offers an idea about the differences between the ecosystems of Gemlik olives in the Akhisar (AO) and Iznik (IO) regions. The study could be useful in characterizing a very important product and, in this way, could help to promote its marketing.

Chemical composition, antibacterial and antifungal activity of the essential oil of Thymbra spicata L. from Turkey.

The composition of the essential oil from aerial parts of Thymbra spicata L. from Turkey was analysed by GC-MS and its in vitro antimicrobial activity was examined. GC-MS analysis of the essential oil resulted in the identification of twenty-three constituents, representing 97.04% of the oil. The major compounds detected in the essential oil were carvacrol (60.39%), gamma-terpinene (12.95%), and p-cymene (9.61%). The in vitro efficacy of the essential oil against 21 bacteria and seven Candida species was examined using disc diffusion and minimum inhibitory concentration (MIC) methods. The essential oil demonstrated strong anti-microbial activity in a wide spectrum against most microorganisms, particularly the yeasts tested. This is the first report on the anticandidal properties of the essential oil of T. spicata. In conclusion, this study confirms that T. spicata essential oil could be considered as a natural antimicrobial source.

Effects of pH and temperature on growth and glycerol production kinetics of two indigenous wine strains of Saccharomyces cerevisiae from Turkey / Efeito do pH e temperatura na cinética de crescimento e da produção de glicerol de duas linhagens vinícolas selvagens de Saccharomyces cerevisiae da Turquia

The study was performed in a batch system in order to determine the effects of pH and temperature on growth and glycerol production kinetics of two indigenous wine yeast strains Saccharomyces cerevisiae Kalecik 1 and Narince 3. The highest values of dry mass and specific growth rate were obtained at pH 4.00 for both of the strains. Maximum specific glycerol production rates were obtained at pH 5.92 and 6.27 for the strains Kalecik 1 and Narince 3, respectively. Kalecik 1 strain produced maximum 8.8 gL-1 of glycerol at pH 6.46. Maximum glycerol concentration obtained by the strain Narince 3 was 9.1 gL-1 at pH 6.48. Both yeasts reached maximum specific growth rate at 30ºC. Optimum temperature range for glycerol production was determined as 25-30ºC for the strain Kalecik 1. The strain Narince 3 reached maximum specific glycerol production rate at 30ºC. Maximum glycerol concentrations at 30ºC were obtained as 8.5 and 7.6 gL-1 for Kalecik 1 and Narince 3, respectively.

Este estudo foi conduzido em sistema descontínuo a fim de determinar o efeito do pH e da temperatura na cinética de crescimento celular ede produção de glicerol de duas linhagens selvagens de vinificação, Saccharomyces cerevisiae Kalecik 1 e Saccharomyces cerevisiae Narince 3. Os maiores valores de massa celular seca e de velocidade específica de crescimento foram obtidos em pH 4,0 para as duas linhagens. A máxima velocidade específica de produção de glicerol foi obtida em pH 5,92 e 6,27 para a linhagem Kalecik 1 e Narince 3, respectivamente. A linhagem Kalecik 1 proporcionou a máxima produção de glicerol, 8,8 gL-1 em pH 6,46. A máxima concentração de glicerol obtida pela linhagem Narince 3 foi de 9,1 gL-1 no pH 6,48. As duas linhagens atingiram a máxima velocidade específica de crescimento à temperatura de 30ºC. A faixa de temperatura ótima para a produção de glicerol para a linhagem Kalecik 1 variou de 25 a 30ºC. A linhagem Narince 3 atingiu a máxima velocidade específica de produção de glicerol a 30ºC. A máxima concentração de glicerol, obtida a 30ºC, foi de 8,5 e 7,6 gL-1 para as linhagens Kalecik 1 e Narince 3, respectivamente.