β‐Galactosidases produced by microorganisms are being used in food technology for hydrolysis of lactose in milk and milk by‐products. The enzyme has attracted much attention in view of lactose intolerance in human population and due to importance of milk in human diet. β‐Galactosidase hydrolyze β‐galactopyranosides, that is, lactose, and form a range of trans‐galactosylation products or galactooligosaccharides (GOS) capable of providing several health benefits as prebiotics. In addition, the enzyme also finds applications in production of lactose based sweeteners from high lactose containing effluents of cheese manufacturing industries. Currently, the enzyme is mainly obtained from Aspergillus niger and Kluyveromyces lactis, however, they are thermolabile with optimum pH between 4.0 and 6.0 accompanied by low chemical resistance and high product inhibition properties. Thermostable enzymes are suitable to perform the hydrolytic process at relatively high temperatures, minimizing pathogen contamination, psychrophilic β‐galactosidases are preferred for treatment of milk under refrigerated conditions (<15°C), without heating and maintenance of temperature. Lactic acid bacteria (LAB) are a potential source of food grade enzymes and other metabolites. Although reports on the use of β‐galactosidase of LAB in pure form is reported for hydrolysis of lactose in milk and production of fermented milk products for reduced lactose content, methods of immobilization for use in continuous bioreactors are less explored. Recombinant DNA technology has attained much significance to reveal molecular aspects of enzyme catalysis, protein structure, gene organization for expression, and enhancement of thermophilic, psychrophilic, and mesophilic β‐galactosidases. Heterologous expression of extremozymes with β‐galactosidase would help in overcoming the limitations faced within the bioprocess technology. Practical applications Lactic acid bacteria (LAB) producing extracellular cell bound β‐galactosidase have been isolated and enzyme production was carried out using modified MRS medium incorporating lactose as enzyme inducer. Process for growing probiotic lactic acid bacteria for β‐galactosidase from fermented milk products has been patented (Indian Patent No. 247904). Thermostable β‐galactosidases were also extracted from Kluyveromyces lactis a yeast, isolated from curd samples and Bacillus sp. MTCC 864. An Indian patent has been granted for a simple, cost effective perforated two compartment immobilized enzyme bioreactor was designed and fabricated for lactose hydrolysis (Indian Patent No. 264609). The bioreactor can be operated continuously at temperature between 5.0 and 75.0°C, employing different immobilized enzyme preparations for different operational temperatures. β‐galactosidase of cell confined LAB and yeast have been immobilized in agarose and galactooligosaccharides (GOS) production was observed at 40% lactose concentration in 0.05M phosphate buffer at pH 6.5. Immobilized bioreactor preparation could be used for lactos...

Polyhydroxybutyrate (PHB) was produced by Bacillus mycoides DFC 1, isolated from garden soil. Antimicrobial (AM) films of PHB were prepared by incorporating vanillin (4-hydroxy-3-methoxybenzaldehyde) from 10 to 200 μg/g of PHB. The films were assessed for antimicrobial activity against foodborne pathogens and spoilage bacteria comprising of Escherichia coli, Salmonella typhimurium, Shigella flexneri, and Staphylococcus aureus and fungi such as Aspergillus flavus, Aspergillus fumigatus, Aspergillus niger, Aspergillus parasiticus, Aspergillus ochraceus, Penicillium viridicatum, and Penicillium clavigerum. The minimum concentration of vanillin required to exhibit antimicrobial activity was ≥80 μg/g PHB for bacteria and ≥50 μg/g PHB for fungi. The PHB films with and without vanillin were studied for mechanical and thermal properties such as tensile strength, Young's modulus, percentage elongation to break, melting temperature, and heat of fusion. The thermal stability of the films was studied using thermogravimetric analysis. The release kinetics of vanillin into food matrices was also checked using food stimulants. The study is intended to find applications for PHB films containing vanillin to enhance the shelf life of foods in the form of biodegradable wrapper.

Fructooligosaccharides (FOS) and levan attract much attention due to a wide range of applications in food technology and pharmaceutical and cosmetic industry. Bacillus licheniformis ANT 179, isolated from Antarctica soil, produced levansucrase and levan in a medium containing sucrose as carbon substrate. In this study, characterization of levansucrase and production of short-chain FOS and levan were investigated. Temperature and pH optimum of the enzyme were found to be 60 °C and pH 6.0, respectively. The optimization of fermentation conditions for levan production using sugarcane juice by response surface methodology (RSM) was carried out. Central composite rotatable design was used to study the main and the interactive effects of medium components: sugarcane juice and casein peptone concentration on levan production by the bacterium. The optimized medium with sugarcane juice at 20 % (v/v) and casein peptone at 2 % (w/v) was found to be optimal at an initial pH of 7.0 and incubation temperature of 35 °C for 48 h. Under these conditions, the maximum levan concentration was 50.25 g/L on wet weight basis and 16.35 g/L on dry weight basis. The produced inulin type FOS (kestose and neokestose) and levan were characterized by Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance (NMR) analysis. The study revealed that the levansucrase could form FOS from sucrose. The locally available low-cost substrate such as sugarcane juice in the form of a renewable substrate is proposed to be suitable even for scale-up production of enzyme and FOS for industrial applications. The levan and FOS synthesized by the bacterium are suitable for food applications and biomedical uses as the bacterium has GRAS status and devoid of endotoxin as compared to other Gram-negative bacteria.

Bacteria produce poly (γ‐glutamic acid) (γ‐PGA), a polymer of l‐ or d‐glutamic acid, as a defense response and have gained importance due to their applications in food and pharmaceutical industry. In the present investigation, production of γ‐PGA using cost‐effective carbon substrate, characterization of the produced polymer, and its application as cryoprotectant for selected freeze‐dried probiotic bacteria were investigated. Central composite rotatable design of response surface methodology was used to study the main and the interactive effects of medium components: rice bran and casein peptone concentration. Rice bran at 35% (w/v) and casein peptone at 7.5% (w/v) were found to be optimal at an initial pH of 7.5, and incubation temperature of 37°C for 48 H produced 8.2 g/L γ‐PGA on dry weight basis. The thermal properties such as melting temperature, heat of fusion, and thermal stability were also studied. Ten percent (w/v) of γ‐PGA with 10 percent of sodium alginate (w/v) protected viability of Bifidiobacterium bifidum NCDC 235 and B. adolescentis NCDC 236 during freeze drying at –80 ˚C for 48 H. The γ‐PGA synthesized by the reported bacterium with GRAS status is suitable for food and biomedical applications.

Effect of addition of bacterial cellulose (BC) and inulin on properties such as melting rate, over run, and sensory properties of ice cream was investigated. BC-supplemented ice creams were characterized by a significant reduction in the melting rate, while inulin contributed to enhance the over run and sensory properties. Sensory perceptions varied for BC at 17% and 30% (wet weight) when compared to inulin addition at 0.7% and 1.4% (dry weight). Eight formulations of ice cream were prepared, varying inulin concentration (0.7 and 1.4 g/100 g), BC concentration (17 and 30 g/100 g), and additional water (13.6 ml/100 ml) and two control samples were prepared. An interaction effect among BC, inulin, and additional water content was found for tested parameters. According to the model obtained, the ice cream formulation with 17 g/100 g BC and 1.4 g/100 g inulin observed significant differences for reduction in melting rate and increased fiber content.How to cite this article: Xavier JR, Ramana KV. Development of slow melting dietary fiber-enriched ice cream formulation using bacterial cellulose and inulin. J Food Process Preserv.