Aims and Scope

(i) Why do we feel that the issue is important and timely? Research in renewable biopolymers as substitutes for full-carbon-backbone plastics from fossil resources presents a topical R&D field worldwide. This is due to the ongoing depletion of fossil resources, the growing piles of plastic waste and plastic pollution of marine environments, and the need to convert waste streams of different industrial origin in a value-added way. PHA have the potential to replace established petro-plastics both in bulk applications as packaging material and in niche applications, such as the medical, electronical, etc. field. Moreover, the close relation of PHA production and application to the food sector becomes more and more evident. Not only does food production provide numerous (ago) industrial by-products which can, on the one hand, be applied to boost growth kinetics of PHA-accumulation strains, as evidenced in the case of nitrogenaceous whey retentate, silage residues, or shrimps waste, and, on the other hand, act as feedstocks for PHA-biosynthesis under nutritionally unbalanced growth conditions, as demonstrated for carbonaceous surplus materials like whey permeate, lignocellulosics, glycerol, waste lipids, etc. Moreover, PHA are currently investigated as future materials contributing to safe and smart food storage and packaging, as shown by PHA´s beneficial gas barrier properties. Grace to the high compatibility of PHA with numerous organic and inorganic additives, a range of promising PHA-based blend of composite materials are accessible to design novel food packaging materials. This encompasses the application of lignocellulosic filler materials from rice, sugar, or wood production, and even the development of more sophisticated formulations resorting to the incorporation of functional nanoparticles into PHA matrixes. (ii) What communities are expected to participate in the Special Issue? Scientific community; Scholars of higher level; Industrialists (iii) How are the background and expertise of the authors relevant to the proposed Special Issue? List of topics for the Special Issue.


Review Article

The Potential of Polyhydroxyalkanoate Production from Food Wastes

Christopher J. Brigham, Sebastian L. Riedel

Applied Food Biotechnology, Vol. 6 No. 1 (2019), , Page 7-18

Background and objective: Over 1 billion tons of foods are wasted every year (not consumed by humans or animals). Most of this waste ends up in landfills. As the global population increases, mankind must look for more sustainable means of living. A recently popular idea is the use of organic wastes as carbon feedstocks for fermentation that produces value added products. Polyhydroxyalkanoates are a family of bio-based, biodegradable polymers that can be produced in large quantities using food and food processing wastes as the main feedstocks. In many cases, biocatalysts have been engineered to efficiently use these waste compounds to produce large quantities of useful intracellular polyhydroxyalkanoates.

Results and conclusion: In the current study, various polyhydroxyalkanoates were produced; each with different thermal and mechanical characteristics useful for different applications. If polyhydroxyalkanoate production facilities are established next to food waste accumulation sites (e.g., large landfills), potentials for the economical and sustainable polyhydroxyalkanoate production sound promising.

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

The Potential Application of Cupriavidus necator as Polyhydroxyalkanoates Producer and Single Cell Protein: A Review on Scientific, Cultural and Religious Perspectives

Jiun Yee Chee, Manoj Lakshmanan, Iffa Farahin Jeepery, Nabila Husna Mohamad Hairudin, Kumar Sudesh

Applied Food Biotechnology, Vol. 6 No. 1 (2019), , Page 19-34

Background and objective: Polyhydroxyalkanoates are environmentally friendly bioplastic compounds produced via the microbial route that offer an alternative to synthetic plastics due to their comparable durability and thermal stability. However, the high production cost as a result of carbon feedstock for microorganisms and the downstream recovery process narrow the usage of polyhydroxyalkanoates in various fields. Conversion of by products from the food and agricultural industries such as waste cooking oil, glycerol, palm sludge oil, oil palm trunk sap and soya waste into polyhydroxyalkanoates is an attractive approach that can minimize and/or add value to waste.

Results and conclusion: Recently, there has been a lot of interest in exploring not just polyhydroxyalkanoates as valued-added products, but also PHA-producing bacteria as a nutritional food or feed source. It has been previously reported that the PHA-producing bacterium, Cupriavidus necator, can be utilized as a single cell protein (SCP) in animal feed owing to its high protein content. The mealworm beetle (Tenebrio molitor) has also been used as the model insect to evaluate the efficacy of Cupriavidus necator cells as a source of protein and to recover polyhydroxyalkanoate granules at the same time. The European Union has imposed strict regulations on the type of feedstock that can be used to ensure that the food chain is safe. In addition, there are religious and cultural concerns. This review will focus on the nutritional value of Cupriavidus necator as single cell protein and its safety as animal feed. The impact of using by-products from the agriculture and food industries as carbon feedstocks to produce single cell protein will be discussed, alongside societal acceptance of this practice.

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

Original Article

Biocomposites Based on Polyhydroxyalkanoates and Natural Fibres from Renewable Byproducts

Patrizia Cinelli, Norma Mallegni, Vito Gigante, Angela Montanari, Maurizia Seggiani, Maria Beatrice Coltelli, Simona Bronco, Andrea Lazzeri

Applied Food Biotechnology, Vol. 6 No. 1 (2019), , Page 35-43

Background and Objective: The use of biopolyesters and natural fibres or fillers for production of biobased composites has attracted interest of various application sectors ranging from packaging to automotive components and other high value applications in agreement with a bioeconomy approach. In the present paper biobased composites were produced by using compostable polymers degradable even in soil and marine water such as polyhydroxyalkanoates with natural fibres or fillers derived by food wastes (legumes by-products) and by wood industry.

Material and Methods: Polyhydroxyalkanoates were processed with a biobased, biodegradable plasticizer such as acetyltributylcitrate and calcium carbonate as inorganic filler. The selected polymeric matrix was used for the production of composites with variable amounts of natural fibres. Green composites were manufactured by extrusion and injection moulding. Thermal, rheological, mechanical and morphological characterizations of the developed composites were performed.

Results and Conclusion: The bio composites properties match the requirements for production of rigid food packaging or other single use items where the market is looking for more sustainable solutions versus the products actually used and hardly recyclable, opening a route for valorization of food residue. Pukanzsky’s model predicts with good accuracy the tensile behavior of the composites showing a medium intensity adhesion between fibres and polymer matrix in both cases analyzed.

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


Bacterial Production of PHAs from Lipid-Rich by-Products

Lorenzo Favaro, Marina Basaglia, Jesus Enrique Gamero Rodriguez, Andrea Morelli, Omodele Ibraheem, Valentino Pizzocchero, Sergio Casella

Applied Food Biotechnology, Vol. 6 No. 1 (2019), , Page 45-52

Background and Objective: Due to oil shortage and environmental problems, synthetic plastics will surely be replaced by alternative, biodegradable materials. A possible good example could be polyhydroxyalkanoates, and the inexpensive agricultural fatty byproducts could be usefully converted to polyhydroxyalkanoates by properly selected and/or developed microbes.

Material and Methods: Among the more common by-products available, a variety of lipid-rich residues have been explored as substrate, such as crude glycerol from biodiesel, biodiesel obtained from fatty residues, and, from slaughterhouse, bacon rind, udder and tallow. In this paper, several new isolates and collection PHA-producing microbes have been screened for both lipolytic activities and polyhydroxyalkanoates production. The soil proved to be the most promising mining place to find new interesting microbial species, even better than more specific and selective environments such as slaughterhouses.

Results and Conclusion: Remarkably, two of the collection strains used here, known to be polyhydroxyalkanoates producers, resulted as really promising, being able to grow directly on all the substrates tested and to produce variable amounts of the polymer, including the co-polymers P (3HB-co-3HV).

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

Background and objective: Polyhydroxyalkanoates have drawn significant attention as alternative to petroleum-based plastics; however, their industrial production is still hindered by the costly feed materials. Co-generation of other high-value products in addition to polyhydroxyalkanoate by the same microbial strains can be helpful in alleviating overall production cost up to 50%. This study for the first time demonstrates that polyhydroxyalkanoate and astaxanthin-rich carotenoids can be co-produced by Paracoccus sp. LL1 using waste cooking oil as substrate.

Material and methods: The halophilic strain of Paracoccus sp. LL1 was grown under batch fermentation using mineral media supplemented with 1% (v v-1) waste cooking oil. Different surfactants were used to improve substrate utilization. Polyhydroxyalkanoate obtained after the fermentation was characterized by fluorescent microscopy, gas chromatography, and Fourier Transform Infra-Red spectroscopy.

Results and conclusion: Oil as a substrate, led to 1.0 g l-1 poly (3-hydroxybutyrate-co-3-hydroxyvalerate) with concomitant production of 0.89 mg l-1 of carotenoids after 96 h. An enhancement of 2.7-folds in total cell dry mass was achieved when 0.1% (v v-1) Tween-80 was used as surfactant for ease in oil metabolism. Paracoccus sp. LL1 has the potential to serve as a single cell factory for bioconversion of cheap substrates into high value products.

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

Camelina Oil as a Promising Substrate for mcl-PHA Production in Pseudomonas sp. Cultures

Daniel Bustamante, Marta Tortajada, Daniel Ramon, Antonia Rojas

Applied Food Biotechnology, Vol. 6 No. 1 (2019), , Page 61-70

Background and objective: Polyhydroxyalkanoates are biodegradable polyesters synthesized by some prokaryotic organisms from renewable sources. Medium-chain-length Polyhydroxyalkanoates show interesting properties as elastic and adhesive specialty polymers. Medium-chain-length Polyhydroxyalkanoates producers such as Pseudomonas sp. have demonstrated high yields on fats and oils. Camelina sativa is non-food chain competing crop, whose seed contain about 43% (w w-1) oil in dry matter with about 90% (w w-1) of unsaturated fatty acids. Camelina oil was for the first time tested for the production of medium-chainlength Polyhydroxyalkanoates by different Pseudomonas strains.

Material and methods: The production of Polyhydroxyalkanoate was evaluated in a nitrogen-limited minimal medium supplemented with crude Camelina oil or saponified oil to compare the production capability of Pseudomonas sp. strains. A phosphates-limited medium was used to optimize polyhydroxyalkanoate production in fed-batch assays. Experiments were carried out by duplicates.

Results and conclusion: Pseudomonas resinovorans was used for direct fermentation of Camelina oil without prior hydrolysis. A first approach to process development in bioreactor has provided up to 40% (w w-1) polymer content, matching highest medium-chain-length polyhydroxyalkanoates titer reported from plant oils (13.2 g l-1). Camelina oil was shown to be a suitable substrate for production of medium-chain-length polyhydroxyalkanoates. This non-food vegetable oil gave good results for Pseudomonas resinovorans DSM 21078 without any pre-treatment.

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

Production of Medium-Chain Length Polyhydroxyalkanoates by Pseudomonas citronellolis Grown in Apple Pulp Waste

Ana Teresa Rebocho, Joao Ricardo Pereira, Filomena Freitas, Luisa Alexandra Neves, Vitor Delgado Alves, Chantal Sevrin, Christian Grandfils, Maria A.M. Reis

Applied Food Biotechnology, Vol. 6 No. 1 (2019), , Page 71-82

Background and objective: Apple pulp waste generated by the fruit processing industry is a sugar-rich material with great potential to be used as a feedstock for production of value added microbial products. The aim of this work was to use this feedstock for the cultivation of Pseudomonas citronellolis and production of medium-chain-length polyhydroxyalkanoates, a natural elastomer.

Material and methods: The solid fraction of the apple pulp waste was discarded and the soluble fraction, rich in fructose (17.7 g l-1), glucose (7.5 g l-1) and sucrose (1.2 g l-1), was used for the batch bioreactor cultivation of Pseudomonas citronellolis NRRL B-2504.

Results and conclusion: Pseudomonas citronellolis reached a polymer content in the biomass of 30% wt and a volumetric productivity of 0.025 g l-1 h-1. The polymer was mainly composed of 3-hydroxydecanoate (68% mol) and 3-hydroxyoctanoate (22% mol), with minor contents of 3-hydroxydodecanoate (5% mol), 3-hydroxytetradecanoate (4% mol) and 3-hydroxyhexanoate (1% mol), and had a molecular weight of 3.7×105 Da. It presented glass transition and melting temperatures of -12 and 53°C, respectively, and a thermal degradation temperature of 296°C. The polymer’s films were dense, ductile and permeable to oxygen and carbon dioxide. These results demonstrated that apple pulp waste is a suitable feedstock for the production of a biopolymer with properties that render it a promising alternative to some synthetic petrochemical-derived polyesters.

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

Background and objective: Waste chicken feather is an important waste product of the poultry processing industry and is annually produced in substantial amounts. Hence, wise management of this waste is desirable. In this work we aimed at feathers biodegradation by a selected bacterial strain capable of utilizing chicken feathers as sole carbon source Pseudomonas putida KT2440. To utilize feather, the bacterial culture excrete keratinase, which can be easily isolated after biodegradation process and which, therefore, represents an interesting side product of the intended technology. Moreover, bacterial culture of employed for feather degradation is also capable of mcl-PHA accumulation.

Materials and methods: Bacterial culture of Pseudomonas putida KT2440 was cultivated in presence of waste chicken feathers as the only carbon source; during the cultivation keratinase activity and biomass growth were monitored. Metabolically active biomass after feather degradation was used for mcl-PHA production.

Results and conclusion: During cultivation on waste feathers, bacteria did not accumulate detectable amounts of medium-chain length polyhydroxyalkanoate (mcl-PHA); nevertheless, when metabolically active bacterial cells after feather biodegradation were transferred into nitrogen limited mineral media, a high medium-chain length polyhydroxyalkanoate content of 61% of cell dry weight in microbial cells was reached. The polymer consisted of 3- hydroxyhexanoate (27.2% mol) and 3-hydroxyoctanoate (72.8% mol) monomer units. Therefore, this work demonstrates a possible interconnection of feather biodegradation with keratinase and medium-chain length polyhydroxyalkanoate production.

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