Biodegradation of Hard Keratins by Two Bacillus Strains

Abstract

Background:Extensive quantities of keratinic by-products are disposed annually by animal-processing industry, causing a mounting ecological problem due to extreme resilience of these materials to enzymatic breakdown. There is a growing trend to apply cheap and environment-friendly methods to recycle keratinic wastes. Soil bacteria of profound keratinolytic potential, especially spore-forming rods from the genus Bacillus, play a significant role in keratinase-mediated biodegradation of keratins, therefore could be effective in hastening their biodegradation. Keratin hydrolysis in microbial cultures is one of the most promising techniques not only to utilize this protein but also to obtain valuable by products.Objectives:The study was undertaken to investigate the biodegradation process of various keratinic materials by two Bacillus strains.Materials and Methods:Two keratinolytic strains, Bacillus cereus and B. polymyxa, were subject to cultures in the presence of several keratinic appendages, like chicken feathers, barbs and rachea of ostrich feathers, pig bristle, lamb wool, human hair and stratum corneum of epidermis, as main nutrient sources. Bacterial ability to decompose these waste materials was evaluated, at the background of keratinase and protease biosynthesis, in brief four-day cultures. Keratinolytic activity was measured on soluble keratin preparation and proteases were assayed on casein. Additionally, amounts of liberated proteins, amino acids and thiols were evaluated. Residual keratin weight was tested afterwards.Results:Both tested strains proved to be more adapted for fast biodegradation of feather β-keratins than hair-type α-keratins. B. cereus revealed its significant proteolytic potential, especially on whole chicken feathers (230 PU) and stratum corneum (180 PU), but also on separated barbs and rachea, which appeared to be moderate protease inducers. Keratinolytic activity of B. cereus was comparable on most substrates and maximum level obtained was 11 KU. B. polymyxa was found to be a better producer of keratinases, up to 32 KU on chicken feathers and 14 KU on both fractions of ostrich feathers. Its proteolytic activity was mostly revealed on stratum corneum and human hair. Stratum corneum was extensively degraded by both bacterial strains up to 99% - 87%, chicken feathers 47-56%, ostrich barbs and rachea, 28% and 35% at maximum, respectively. Keratin fibres of structures like human hair, lamb wool and pig bristle remained highly resilient to this short microbiological treatment, however certain extent of keratinase induction was also observed.Conclusions:The obtained results prove that keratinolytic potential of both tested bacterial strains could be applied mainly in biodegradation of feathers, however, B. cereus and B. polymyxa differed in terms of keratinase and protease production on each of the substrates. Biodegradation of highly resilient structures like hair or pig bristle requires further analysis of process conditions.

Impacts of Macronutrients on Gene Expression: Recent Evidence to Understand Productive and Reproductive Performance of Livestock

“…Proteins are the most important macronutrient contributing to the structure of muscles, skin, nails, hairs, wools, and feathers (Laba and Rodziewicz, 2014). Although proteins are not a primary energy source, they can be used as an energy source under specific circumstances.…”

A Statistical-Mathematical Model to Optimize Chicken Feather Waste Bioconversion via Bacillus licheniformis SHG10: A Low Cost Effective and Ecologically Safe Approach

“…The up to date literature contains plethora of feather-degrading microorganisms synonymously called keratinase-producing microorganisms and their keratinolytic enzymes belonging to bacteria ,actinomycetes in majority and fungi in minority [5,7,[16][17][18][19][20][21][22][23]. Seeking for novel microbes with promising feather-degrading capabilities is currently the main concern of numerous researches in this respect [24][25][26][27][28]. It is worth mentioning that directing the process of feather degradation by powerful keratinase-producing microorganisms would help fulfill four indispensable prerequisites: a) environmentally safe bioprocess, b) economically low cost effective bioprocess, c) high nutritionally retained end products and d) high potential feather hydrolysates in numerous industries.…”

Morphological, biochemical and molecular characterization of Bacillus isolates as a producer of industrial enzymes

“…Diğer bir Bacillus türü olan B. licheniformis, deterjan endüstrisi başta olmak üzere biyoyakıt üretimi, pestisit yıkımı ve antibiyotik üretimi gibi uygulamalarda tercih edilmektedir (4,32). Ayrıca son yıllarda keratinaz enzim üretme yeteneklerini kullanarak doğada yaygın bulunan kuş tüylerinin besin değeri yüksek gıdalara dönüştürülmesi konusunda araştırmalar da bulunmaktadır (33). Endüstride hali hazırda kullanılan B. licheniformis suşları ile Y35 izolatının farklı fizyolojik koşullardaki büyüme yetenekleri karşılaştırıldığında sıcaklık ve pH profillerinin benzer olduğu göze çarpmaktadır.…”