Original Article

Characterization of Thermotolerant Acetic Acid Bacteria Isolated from Various Plant Beverages in Thailand

Panadda Charee, Varavut Tanamool, Hirohide Toyama, Wichai Soemphol

Applied Food Biotechnology, Vol. 7 No. 2 (2020), 10 March 2020, Page 61-72


Background and objective: Thermotolerant acetic acid bacteria are more resistant to high temperatures than that other bacteria are. This difference includes 5-10ºC, which decreases high costs of cooling systems needed for the growth of these bacteria while preserving their high productivity. In this study, effective thermotolerant acetic acid bacteria isolated from various fermented plant beverages were characterized for their ability to produce acetic acid and their characteristics were investigated.

Materials and methods: Various thermotolerant acetic acid bacteria isolated from fermented plant beverages samples were investigated for their ability to produce acetic acid at high temperature. Two isolates of Acetobacter pasteurianus were selected and their growth and acetic acid production ability were assessed under various conditions. Furthermore, capsular polysaccharides of these strains were extracted and characterized using gas-liquid chromatography and Fourier-transform infrared spectroscopy.

Results and conclusion: In this study, Acetobacter pasteurianus and Acetobacter tropicalis were dominant thermotolerant acetic acid bacteria in the fermented plant beverage. Two isolates of Acetobacter pasteurianus, Fermented Plant Beverages 2-3 and 2-16, produced acetic acid effectively at 39°C, compared to that Acetobacter pasteurianus SKU1108 did as a superior control for thermotolerant acetic acid bacteria. Fermented Plant Beverage 2-3 was able to completely oxidize 5% v v-1 ethanol to acetic acid at 39°C, while a long lag time was observed at 6% ethanol. However, production of acetic acid was still up to 4% w v-1. Moreover, this isolate exhibited excellent resistance to acetic acid at high temperatures, compared to 2 other strains in liquid and solid media. However capsular polysaccharides isolated from the 3 strains included glucose, rhamnose and galactose. Fourier-transform infrared spectroscopy spectra of capsular polysaccharides from Fermented Plant Beverage 2-3 at 1740 cm-1 identified a clearly different O-acetyl ester. This might be attributed to different O-acetyl ester contents of the capsular polysaccharides and also to resistance to acetic acid and high temperature.

Conflict of interest: The authors declare no conflict of interest.

Evaluating the Feasibility of Poly (3-hydroxybutyrate-co-3-hydroxyvalerate) Co-Biopolymer Production from Rice Wastewater by Azohydromonas lata

Malihe Amini, Samira Sobhani, Habibollah Younesi, Hajar Abyar, Babak Salamatinia, Maedeh Mohammadi

Applied Food Biotechnology, Vol. 7 No. 2 (2020), 10 March 2020, Page 73-83


Background and objective: Biopolymers are environmental friendly, non-toxic renewable alternatives for conventional synthetic polymers. Rice wastewater contains high biochemical and chemical oxygen demands and organic contents mainly in form of starch which can cause serious environmental problems, while, it can be used as a potentially low-cost substrate for biopolymer production. The objective of the current study was to investigate the ability of Azohydromonas lata to produce poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (P3HB-co-P3HV) from rice wastewater in a batch system.

Material and methods: Aspergillus niger was first used to hydrolyze the starch content of rice wastewater to fermentable soluble sugars. Then, the bacterium Azohydromonas lata was cultured in hydrolyzed wastewater at various C: N: P ratios to produce biopolymers. So, effects of different nitrogen and carbon sources on P (3HB) and P (3HV) contents at a C: N: P ratio of 100:4:1 were assessed.

Results and conclusion: This study showed that Azohydromonas lata was able to produce poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (P3HB-co-P3HV) from rice wastewater in the presence of simple carbon sources and under limited nutrient conditions, especially phosphorus. The highest content of P (3HB) was achieved when ammonium sulphate was used as nitrogen source at a C: N: P ratio of 100:4:1. The highest recorded cell dry mass and biopolymer concentration were 4.64 and 2.8 g l-1 respectively, at a P(3HB) content in biomass of 60%
 w w-1. Results indicated that phosphorus and nitrogen limitations could significantly affect P (3HB) production. In general, rice wastewater is a potential alternative for carbon sources such as glucose and maltose in polyhydroxybutyrate production.

Conflict of interest: The authors declare no conflict of interest.

Lipase-Catalyzed Synthesis of Medium-Long-Medium-Type of Structured Lipids from Refined Bleached Deodorized Olein

Qabul Dinanta Utama, Azis Boing Sitanggang, Dede Robiatul Adawiyah, Purwiyatno Hariyadi

Applied Food Biotechnology, Vol. 7 No. 2 (2020), 10 March 2020, Page 85-94


Background and objective: Medium-long-medium type of structured lipid is appropriate for the management of obesity, fat malabsorption and other metabolic disorders. No studies have been carried out on the ability of Lipozyme TL IM in two types of reaction, acidolysis and transesterification for Medium-long-medium type of structured lipids synthesis using refined bleached deodorized olein as major substrate. This study aimed to synthesize medium-long-medium type of structured lipids rich in TAG, especially with equivalent carbon number 32. Furthermore, stability of Lipozyme TL IM in acidolysis and transesterification was assessed.

Materials and methods: Two methods of synthesis, transesterification (tricaprylin and refined bleached deodorized olein) and acidolysis (caprylic acid and refined bleached deodorized olein), were used to produce medium-long-medium type of structured lipid. The synthesis was catalyzed using specific sn-1,3 commercial lipase (Lipozyme TL IM). Composition of triacylglycerol substrates and products and residual activity of the enzyme were investigated.

Results and conclusion: The transesterification needed approximately 4 h to achieve a maximum concentration of equivalent carbon number 32 (16.75%) this was 20 h with an equivalent carbon number 32 concentration of 16.28% for acidolysis. Lipozyme TL IM included a further stable activity for transesterification as its half-life was longer than that of acidolysis. Lipozyme TL IM was appropriate for catalyzing transesterification to produce medium-long-medium type of structured lipid rich in triacylglycerol with equivalent carbon number 32, presumably that of 1,3-dicapryoyl-2-oleoyl-sn-glycerol, compared to that for acidolysis.

Conflict of interest: The authors declare no conflict of interest.

Production of Low-Fat Camel Milk Functional Ice creams Fortified with Camel Milk Casein and its Antioxidant Hydrolysates

Nasim Hajian, Maryam Salami, Mehdi Mohammadian, Maryam Moghadam, Zahra Emam-Djomeh

Applied Food Biotechnology, Vol. 7 No. 2 (2020), 10 March 2020, Page 95-102


Background and objective: The objective of this study was to produce functional low-fat camel milk ice creams enriched with native camel milk casein or its antioxidant hydrolysates produced by chymotrypsin.

Material and methods: Native or hydrolyzed camel milk caseins (0, 2 and 4%) were added to camel milk low-fat ice creams. Hydrolysates were characterized for molecular weights and antioxidant activities. Physical (hardness, overrun and melting resistance) and sensorial attributes of the final products were assessed.

Results and conclusion: Results showed that the chymotrypsin-mediated hydrolysis significantly (P<0.05) increased 2,2′-azinobis (3-ethylbenzthiazoline-6-sulfonic acid) radical scavenging activity of the native camel milk casein. Apparent viscosity and consistency coefficient of the ice creams were increased by addition of proteins and hydrolysates due to their water holding capacity. Protein/hydrolysates-fortified samples showed higher melting resistances but lower overruns and softer textures, compared to control ice creams with no added native or hydrolyzed camel milk casein. Sensory analysis showed that only samples enriched with 2% of casein hydrolysate included sensory properties similar to those of control camel milk low-fat ice creams and other samples received lower sensory scores. Generally, this study has suggested that camel milk can be used to produce low-fat ice creams. Properties of these ice creams can be modified by adding various concentrations of native and hydrolyzed camel milk caseins.

Conflict of interest: The authors declare no conflict of interest.

Production, Recovery and Characterization of an Enterocin with Anti-Listerial Activity Produced by Enterococcus hirae OS1

Samir Ananou, Soukaina Lotfi, Ouarda Azdad, Nehemie Nzoyikorera

Applied Food Biotechnology, Vol. 7 No. 2 (2020), 10 March 2020, Page 103-114


Background and objective: Lactic acid bacteria, used in food processing for a long time, can produce various metabolites during their growth, including bacteriocins. These antimicrobials, used as natural bio-preservatives, enhance the food safety. The objective of this study was to assess lactic acid bacteria bacteriocins with anti-listerial activity and optimize their production and recovery process.

Material and methods: Isolate was identified using conventional assays (morphological and biochemical characteristics) and 16S rRNA gene sequencing. Lactic acid bacteria bacteriocins were characterized based on their physicochemical properties (nature, pH stability and thermo-resistance). The production process was based on optimization of media components (growth media and addition of glucose, nitrogen source and tween 20) and culture conditions (temperature, pH, agitation and inoculum size). Furthermore, optimization of the recovery process was studied using ion exchange chromatography on amberlite IRC-50 (effects of resin size and NaCl eluent concentration).

Results and conclusion: Enterococcus hirae OS1 was isolated from Moroccan raw cow milk as bacteriocinogenic strain. After optimization of the bacteriocin production process, results showed that the key parameters for increasing of production included temperature of 30°C, pH of 6.5 and inoculum size of 5%. Production with whey-based and economic food-grade substrate allowed high production of enterocin OS1 (1,600 AU ml-1) (P<0.001). Simultaneous addition of glucose (1%) and Tween 20 (1%) increased enterocin titer significantly (5,866 AU ml-1) (P<0.01). Recovery efficiency increased with use of 70% amberlite IRC-50 resin and elution with 2M NaCl. Indeed, recovery of 75.4% of bacteriocin was achieved in comparison to 15.7% of bacteriocin without optimization. This promises achieving high quantities of enterocin at low costs.

Conflict of interest: The authors declare no conflict of interest.

Optimizing Growth Conditions of Kluyveromyces marxianus for Mannan Production as a Bioemulsifier

Ashraf Hajhosseini, Delaram Doroud, Anoosheh Sharifan, Zohreh Eftekhari

Applied Food Biotechnology, Vol. 7 No. 2 (2020), 10 March 2020, Page 115-126


Background and objective: Mannan which is a linear glycoprotein with β-1,4 links carrying mannose units bind to proteins, includes natural amphiphiles and serves as a bioemulsifier. The aim of this study was optimization of growth and purification of Kluyveromyces marxianus for mannan production, which can use as a natural bioemulisifier.

Material and methods: In this study, mannan production by Kluyveromyces marxianus was assessed using combinational method of fractional factorial design and response surface methodology optimization. Process variables include concentration of carbon source (15, 30, 45 g l-1) of glucose, and glycerol and methanol at 0, 2.5 and 5 gl-1), nitrogen source (yeast extract and peptone 4, 6 and 8 gl-1), as well as fermentation time (48, 96 and 144 h), pH (4, 6, 8) and agitation speed (150, 200 and 250 rpm).

Results and conclusion: Results showed that four variables of carbon and nitrogen source concentrations, as well as fermentation time and pH included the greatest effects on mannan production. Optimization of the affecting factors using response surface methodology demonstrated appropriate conditions of mannan production by Kluyveromyces marxianus as 55.15 g l-1 of glucose, 9.35 g l-1 of yeast extract, pH of 4.99 and fermentation time of 168 h, which led to a mannan yield of 245.98 mg (100 ml)-1culture media.

Conflict of interest: The authors declare no conflict of interest.