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Polyhydroxyalkanoates (PHAs) are the biopolymer of choice if we look for a substitute of petroleum-based non-biodegradable plastics. Microbial production of PHAs as carbon reserves has been studied for decades and PHAs are gaining attention for a wide range of applications in various fields. Still, their uneconomical production is the major concern largely attributed to high cost of organic substrates for PHA producing heterotrophic bacteria. Therefore, microalgae/cyanobacteria, being photoautotrophic, prove to have an edge over heterotrophic bacteria. They have minimal metabolic requirements, such as inorganic nutrients (CO2, N, P, etc.) and light, and they can survive under adverse environmental conditions. PHA production under photoautotrophic conditions has been reported from cyanobacteria, the only candidate among prokaryotes, and few of the eukaryotic microalgae. However, an efficient cultivation system is still required for photoautotrophic PHA production to overcome the limitations associated with (1) stringent management of closed photobioreactors and (2) optimization of monoculture in open pond culture. Thus, a hybrid system is a necessity, involving the participation of microalgae/cyanobacteria and bacteria, i.e., both photoautotrophic and heterotrophic components having mutual interactive benefits for each other under different cultivation regime, e.g., mixotrophic, successive two modules, consortium based, etc. Along with this, further strategies like optimization of culture conditions (N, P, light exposure, CO2 dynamics, etc.), bioengineering, efficient downstream processes, and the application of mathematical/network modeling of metabolic pathways to improve PHA production are the key areas discussed here. Conclusively, this review aims to critically analyze cyanobacteria as PHA producers and proposes economically sustainable production of PHA from microbial autotrophs and heterotrophs in “hybrid biological system.”

Tuberculosis (TB) is caused by Mycobacterium tuberculosis (Mtb) bacteria. This disease is still a worldwide threat as it remains one of the leading causes of death in the world. Almost one-third of the world population is still infected by the Mtb bacteria either causing Latent TB or Active TB. In spite of huge progress in medical sciences with the latest prevention and treatment techniques, it is still a big threat to human beings. Possibly, there are several reasons behind the existence and survival of these Mtb bacteria depending upon the standard of living or the medical history of the person. Different people are treated in a different manner according to their conditions, which is strictly followed by the norms fixed by the government. Till date, there is limited research in the field of modeling clinical diagnosis path in TB; hence, it requires a full interplay between diagnosis and treatment. This motivated us to use a Discrete Event System (DES), Petri net, to model the diagnostic path as it helps to understand the structural and behavioral properties of the process. In this chapter, we are modeling the clinical diagnosis path of TB considering some important aspects within the process with the use of a graphical tool, Petri net. The modeling and analysis of the diagnostic path help to find and validate the longest and shortest methods to treat tuberculosis.

Mathematical modeling is playing a very important role in clarifying, analyzing, and drawing of qualitative and quantitative results. In almost every area of sciences, the complex system is being modeled using some mathematical modeling using a graphical approach, differential equation approach, statistical approach, and many more. In this chapter, we are focusing on the graphical approach using Petri Nets (PN). Petri net came in focus in the early ‘90s after Carl Adam introduced this method in his Ph.D. thesis. By then, it is being widely used to model the complex systems in engineering, computational, biological, and many more fields. Initially, it was accounted as a modeling tool in Computer Science (CS), but later, PN method started to model systems in Automatic Control (AC) too for automation after that it was being used in the background of Operations Research (OR). Therefore, this method recognized as the Discrete Event Dynamic Systems (DEDS) theory, at the intersection of CS, AC, and OR. Moreover, different kinds of hybrid PNs like Time Petri Net (TPN), Stochastic Petri Net (SPN) are being extensively studied today. PN is also being proved to be a useful tool to model the biological system like cell cycle, pathways in diseases to treat, and many more. It will help to find several structural and behavioral properties of the system.

Alcoholism is ranked as the third largest impact on human health and it leads to Alcohol-Related Brain Damage. However, in this study, we have used graph theory metrics in Igraph software to analyze the functional connectivity of the EEG network of 20 alcoholic and 20 healthy volunteers. The graph-theoretic analysis shows, compared with healthy control group, the brain network of an alcoholic has a smaller mean degree, larger degree centrality, smaller modularity, larger transitivity, larger global efficiency, larger assortativity, larger average path length, smaller network diameter but same small-world properties. The Alcoholic network lacks functionality, robustness, resilience and linear network. The alcoholic subject has disturbed connectivity in its brain network that leads to Alcohol-Related Brain Damage. This conclusion leads us to new perspective for Alcohol-Related Brain Damage.

Petroleum based synthetic plastics are an integral part of our daily life. However, their excessive usage has resulted in environmental pollution. The primary reason for this pollution is due to their non-biodegradable nature. On the other hand, polyhydroxyalkanoates (PHAs) are biodegradable polymers, which have been shown to be produced by a wide range of bacteria. The unique feature of this bioplastic production is that they can be produced from renewable substrate materials through a unique metabolic route. These PHAs have the potential to replace petroleum based synthetic plastics. PHAs have high commercial value which make them suitable agent for industrial and medical applications. Although simpler and monomeric forms of PHAs have limited biotechnological applications, however, modified forms of PHA can be used in various medical applications such as, drug delivery, biodegradable implants, anticancer agent, and tissue engineering etc. Among all, tissue engineering has emerged globally to improve the current therapeutic approaches, entailing a revolution in clinical practice. PHAs offer several benefits in tissue engineering. These chemically modified biopolymers can be used in tissue repair, regeneration of tissue, scaffolds preparation etc.

Bio-polymers are widely synthesized by living organisms to assist several biological functions. Bacterial biopolymers are produced as a polyhydroxyalkanoates (PHA) in the form intracellular cellular storage material under the nutrient limiting or stress conditions in the excess of carbon source and recognized as a suitable alternative to petrochemical-based synthetic plastic due to their biodegradable and eco-friendly nature. Primarily, the synthesis of PHA is considered as costly process due to the high price of feed and its poor grade of thermal and mechanical properties of homopolymers such as polyhydroxybutyrate. The modification of PHA through chemical or biological synthesis and as composite materials through the incorporation of nanoparticles or other substrate and materials seems viable approaches to improve the properties of PHA for the novel application in the area of biomedical applications including anti-microbial agents. In this book chapter, we are evaluating the potential application of PHA, derivatives of PHA and modified with composite materials as anti-microbial agents.

Drug delivery systems based on biodegradable biomaterials have proved attractive to improve their efficacy. Biopolymers such as Polyhydroxyalkanoates (PHAs) have the potential to be used as materials for preparing nanoparticles as drug carriers. This review describes the recent developments in drug delivery systems based on PHAs derived from microbial fermentations. Various strategies for the synthesis of microspheres, encapsulations, nano-constructs, have been presented, with their potential applications in medical domain.

The synthetic polymers – plastics have been applied in a wide range of activities of our daily routine. However, extensive usage and their non-biodegradable nature have led to their accumulation in quantities, which are difficult to manage and a major cause of environmental pollution. Bacteria have the ability to accumulate Carbon (C) as biopolymers especially under stress conditions. The biopolymers – polyhydroxyalkanotes (PHAs) are biodegradable and have properties quite close to those possessed by plastics. PHAs have been explored in diverse fields including agriculture and medical. In the field of medicine, PHAs hold greater promise because of their usage in producing high value products, in addition to their biodegradable, biocompatible, and non-toxic nature. PHAs have been explored for their role as implants, drug carriers, tissue engineering, biocontrol agents, inhibitors of cancerous growth, and memory enhancing molecules.

Ecobiotechnological approach is an attractive and economical strategy to enrich beneficial microbes on waste biomass for production of Polyhydroxyalkanoate (PHA). Here, six strains of Bacillus spp. were used to produce co-polymers of PHA from pea-shells. Of the 57 mixed bacterial cultures (BCs) screened, two of the BCs, designated as 5BC1 and 5BC2, each containing 5 strains could produce PHA co-polymer at the rate of 505–560 mg/l from feed consisting of pea-shell slurry (PSS, 2 % total solids) and 1 % glucose (w/v). Co-polymer production was enhanced from 65–560 mg/l on untreated PSS to 1,610–1,645 mg/l from PSS treated with defined hydrolytic bacteria and 1 % glucose. Supplementation of the PSS hydrolysate with sodium propionate enabled 5BC1 to produce co-polymer P(3HB-co-3HV) with a 3HV content up to 13 % and a concomitant 1.46-fold enhancement in PHA yield. Using the principles of ecobiotechnology, this is the first demonstration of PHA co-polymer production by defined co-cultures of Bacillus from biowaste as feed under non-axenic conditions. Electronic supplementary material The online version of this article (doi:10.1007/s12088-014-0457-9) contains supplementary material, which is available to authorized users.

Biological hydrogen (H2) and polyhydroxybutyrate (PHB) production from biowaste as feed were investigated with different bacteria. The 23 bacterial strains used in different combinations belonged to - Bacillus spp., Bordetella avium, Enterobacter aerogenes, Proteus mirabilis and a marine bacterium. Defined mixed H2-producers alone could evolve 140–145 mL H2 from 250 mL PSS (Pea-shells slurry). PSS hydrolysed with defined hydrolytic bacterial mixture followed by H2-producers resulted in the production of 5.2 L H2 from 4 L PSS. It was equivalent to a yield of 65 L H2 kg−1 TS fed. Here, H2 constituted 55.2% of the total biogas. On the other hand, Bacillus cereus EGU44 could produce 1685 mg PHB L−1 from prehydrolyzed PSS, which was equivalent to 62.5 g kg−1 TS fed. This is first report of its kind on the use of defined bacterial cultures for each of these steps. This approach of using defined mixed cultures is expected to enhance the sustainability of the process by enhancing their chances of survival in comparison to single bacterial culture. The use of biowaste as feed can further improve the economics of the process.

Aim: To test the Bacillus strains for their abilities to produce polyhydroxybutyrate (PHB) from different sugars and biowaste (Pea-shells). Methods and Results: Six Bacillus strains were checked for their ability to produce PHB from GM2 medium supplemented with different sugars at the rate of 1% (w/v) and from biowaste and GM2 (BW : M) combinations (3 : 7, 1 : 1, 7 : 3). Glucose supplemented GM2 medium resulted in maximum PHB production of 435 mg l−1 constituting 31–62% w/w of the total cell dry mass. Substituting GM2 medium to the extent of 50% with biowaste (pea-shell slurry) resulted in 945–1205 mg l−1 PHB (55–65% w/w). Optimization for additional nitrogen supplementation, inoculum size resulted in a final PHB production of 3010–3370 mg l−1 equivalent to 300 g kg−1 biowaste (dry wt). Conclusion: The Bacillus strains were able to produce PHB from biowaste (Pea-shells) as cheap source of substrate. Significance and Impact of the Study: This is the first report on usage of pea-shells as feed for PHB production, opening new possibilities for its use for production of PHB and Bacillus as potential candidate for the purpose.

Polyhydroxyalkanoates (PHAs) as an alternative to synthetic plastics have been gaining increasing attention. Being natural in their origin, PHAs are completely biodegradable and eco-friendly. However, consistent efforts to exploit this biopolymer over the last few decades have not been able to pull PHAs out of their nascent stage, inspite of being the favorite of the commercial world. The major limitations are: (1) the high production cost, which is due to the high cost of the feed and (2) poor thermal and mechanical properties of polyhydroxybutyrate (PHB), the most commonly produced PHAs. PHAs have the physicochemical properties which are quite comparable to petroleum based plastics, but PHB being homopolymers are quite brittle, less elastic and have thermal properties which are not suitable for processing them into sturdy products. These properties, including melting point (Tm), glass transition temperature (Tg), elastic modulus, tensile strength, elongation etc. can be improved by varying the monomeric composition and molecular weight. These enhanced characteristics can be achieved by modifications in the types of substrates, feeding strategies, culture conditions and/or genetic manipulations.

Carbohydrates especially sugars are employed for the production of different bio-products. Biological waste(s) originating from agricultural, industrial, and municipal sources has been considered as suitable low-cost feed for the production of biofuels and biopolymers. Single-stage production of these bio-products does not lead to complete utilization of organic matter of the biowaste(s) used as feed. Recently, approaches to integrate bioprocesses leading to hydrogen (H2), polyhydroxyalkanoate (PHA), and methane production are gaining importance to metabolize more than 80 % of the biowastes. Integration of H2 and PHA has been proposed but has not been widely studied. Here, we are evaluating the feasibility of integrating H2 and PHA production systems. A further integration of these processes with methanogenesis might be a suitable approach in the near future for overall efficiency.

Integrative processes for the production of bioenergy and biopolymers are gaining importance in recent years as alternatives to fossil fuels and synthetic plastics. In the present study, Bacillus thuringiensis strain EGU45 has been used to generate hydrogen (H2), polyhydroxybutyrate (PHB) and new co-polymers (NP). Under batch culture conditions with 250 ml synthetic media, B. thuringiensis EGU45 produced up to 0.58 mol H2/mol of glucose. Effluent from the H2 production stage was incubated under shaking conditions leading to the production of PHB up to 95 mg/l along with NP of levulinic acid up to 190 mg/l. A twofold to fourfold enhancement in PHB and up to 1.5 fold increase in NP yields was observed on synthetic medium (mixture of M-9+GM-2 medium in 1:1 ratio) containing at 1–2 % glucose concentration. The novelty of this work lies in developing modified physiological conditions, which induce bacterial culture to produce NP.

Metabolic activities of four Bacillus strains to transform glucose into hydrogen (H(2)) and polyhydroxybutyrate (PHB) in two stages were investigated in this study. Under batch culture conditions, Bacillus thuringiensis EGU45 and Bacillus cereus EGU44 evolved 1.67-1.92 mol H(2)/mol glucose, respectively during the initial 3 days of incubation at 37°C. In the next 2 days, the residual glucose solutions along with B. thuringiensis EGU45 shaken at 200 rpm was found to produce PHB yield of 11.3% of dry cell mass. This is the first report among the non-photosynthetic microbes, where the Bacillus spp.-B. thuringiensis and B. cereus strains have been shown to produce H(2) and PHB in same medium under different conditions.

Polyhydroxyalkanoates (PHAs) are biodegradable polymers produced by microbes to overcome environmental stress. Commercial production of PHAs is limited by the high cost of production compared to conventional plastics. Another hindrance is the brittle nature and low strength of polyhydroxybutyrate (PHB), the most widely studied PHA. The needs are to produce PHAs, which have better elastomeric properties suitable for biomedical applications, preferably from inexpensive renewable sources to reduce cost. Certain unique properties of Bacillus subtilis such as lack of the toxic lipo-polysaccharides, expression of self-lysing genes on completion of PHA biosynthetic process – for easy and timely recovery, usage of biowastes as feed enable it to compete as potential candidate for commercial production of PHA.