ORIGINAL ARTICLE Production of polyhydroxybutyrate (PHB) by a novel Klebsiella pneumoniae strain using low-cost media from fruit peel residues A. Valdez-Calderón 1 & M. Barraza-Salas 2 & M. Quezada-Cruz 3 & M. A. Islas-Ponce 1,2 & A. F. Angeles-Padilla 1 & S. Carrillo-Ibarra 4 & M. Rodríguez 5 & N. G. Rojas-Avelizapa 6 & A. Garrido-Hernández 3 & A. M. Rivas-Castillo 1 Received: 26 May 2020 /Revised: 5 November 2020 /Accepted: 13 November 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020 Abstract Plastics are widely used for various applications. Once discarded, it is commonly known that they represent a high environmental threat due to their slow degradation; for this reason, there is an imminent need to replace these products with eco-friendlier ones. In the present work, four bacterial polyhydroxybutyrate (PHB) producers, two consortia, and two isolated strains were success- fully recovered from the facilities of a paper-manufacturing industry. Spectroscopic studies of the biopolymers obtained from these bacteria corroborated their PHB production capabilities, ranging from 4.04 ± 0.16 to 23.82 ± 3.39 g/L. The characterization of the isolate that presented the highest production yield initially coded as E22 led to the identification of a Klebsiella pneumoniae strain, which, compared with other PHA bacterial producers reported to date, could be considered with high production potential. The strain E22 was grown in 5 different media prepared from fruit peel residues of banana, orange, papaya, watermelon, and melon, to determine its growth and PHA production capabilities in these low-cost media. The results obtained show different bacterial growth yields among the media tested, although PHB production yields and productivities were similar in all these low- cost media. Cellular accumulation of the biopolymer was higher in watermelon peel medium (8.4 × 10 -10 g/CFU). These results reveal the potential of K. pneumoniae E22 for PHB production applications and establish encouraging alternatives to be broader explored regarding low-cost media that could enhance the scale-up of bacterial PHA production processes. Keywords Polyhydroxyalkanoates . PHB . Biopolymers . Klebsiella pneumoniae . Fruit residues 1 Introduction Plastic materials are widely used in our daily life, and their usage seems unavoidable due to the diversity and versatility of their properties [1–3]. Because of the difficulties associated with plastic degradation, it is an imminent environmental need to replace these kinds of products with eco-friendlier ones. One alternative is polyhydroxyalkanoates (PHA), a family of biodegradable polyesters of 3-, 4-, 5-, and 6-hydroxyl acids, which are naturally produced by microorganisms through the fermentation process of sugars, hydrocarbons, and lipids [4]. It is known that PHA physical and thermal properties are a function of their subunit composition and that they can present relatively similar properties to conventional polymers [5]. Among PHA, poly-(3-hydroxybutyrates) (PHB) are the most widespread and best-characterized members, synthe- sized by a large number of bacteria as a storage material. These homopolymers contain four carbon subunits of 3- hydroxybutyrate (3HB). They have semi-crystalline behavior (> 50%) with brittle and stiff properties as well as optical * A. M. Rivas-Castillo a.rivas@utvam.edu.mx 1 Universidad Tecnológica de la Zona Metropolitana del Valle de México, Blvd. Miguel Hidalgo y Costilla 5, Los Héroes de Tizayuca, 43816 Tizayuca, Hidalgo, Mexico 2 Facultad de Ciencias Químicas, Universidad Juárez del estado de Durango, Av. Veterinaria S/N, Circuito Universitario, Valle del Sur, 34120 Durango, Mexico 3 División de Químico-Biológicas, Universidad Tecnológica de Tecámac, Km 37.5 Carretera Federal México-Pachuca, Colonia Sierra Hermosa, 55740 Tecámac, Estado de México, Mexico 4 Escuela de Ciencias de la Salud, Universidad del Valle de México, Campus Zapopan, Periférico Poniente 7900, Col. Jardines de Collí, 45010 Zapopan, Jalisco, Mexico 5 Grupo de Propiedades Ópticas de la Materia, Centro de Investigaciones en Óptica, A. P. 1-948, 37000 León, Guanajuato, Mexico 6 Centro de Investigación en Ciencia Aplicada y Tecnología Avanzada del IPN, Cerro Blanco 141, Col. Colinas del Cimatario, 76090 Querétaro, Mexico Biomass Conversion and Biorefinery https://doi.org/10.1007/s13399-020-01147-5