Research
Johnson's research has focused on toxicology and microbiology,with a particular focus on investigating the utilization of Phaffia rhodozyma yeast for astaxanthin production,studying different Clostridium strains,including Clostridium botulinum,and exploring the properties and applications of botulinum toxin. [8]
Botulinum therapy
Johnson's research in toxicology has revealed insights into the properties,uses,and administration of botulinum toxin and other microbial neurotoxins in medicine,highlighting their implications. [9] He,in collaboration with Edward J. Schantz,produced the first FDA-approved batch of botox,and developed Chemistry,Manufacturing,and Control (CMC) procedures for manufacture of botox,enabling its approval by the FDA on the last day of 1989. More specifically,he contributed to the purification and standardization of botulinum toxin preparations,as well as determined critical manufacturing and testing steps for FDA approval in initial strabismus studies. [3] Having explored botulinum toxin therapy for regional movement disorders,he investigated dosage limitations to mitigate immunologic resistance associated with repeated high-dose injections,proposing a threshold of 100 LD50 units or less per injection cycle. [10] Additionally,he explored different immunotypes of botulinum toxin,aiming to increase specific activity to reduce antigen exposure and prevent immunoresistance in human therapy. He made contributions by serving on a team that identified SV2 as the protein receptor for botulinum neurotoxin A,demonstrating its binding mechanism and the impact of SV2 expression on toxin entry. [11] Furthermore,he highlighted advancements in botulinum treatment systems,explored new indication areas,addressed challenges in therapy,and emphasized the importance of drug development projects and enhanced accessibility. [12]
Clostridium botulinum strains
Johnson has conducted research on Clostridium botulinum strains. In 2001,he examined the production of neurotoxin (BoNT) by Clostridium botulinum,shedding light on the regulatory factors involved in neurotoxigenic clostridia. [13] Additionally,he investigated the cellulase system of Clostridium thermocellum,demonstrating comparable solubilization rates to Trichoderma reesei. [14] His focus extended to exploring the therapeutic potential of clostridial toxins,particularly botulinum toxin,for various diseases. He emphasized the abundance of protein toxins in clostridia and proposed solutions to address the limitations of botulinum toxin. [15] Furthermore,he developed a minimal chemically defined medium for the growth of Clostridium thermocellum,identifying specific growth factors such as biotin,pyridoxamine,vitamin B(12),and p-aminobenzoic acid. [16] His research on Clostridium botulinum and Clostridium thermocellum improved understanding of clostridial metabolism,growth media,and cellulose degradation. Studying Clostridium botulinum strains Hall A,Okra B,and Iwanai E,he identified minimal nutritional requirements,advancing our understanding of essential nutrients and defined media for specific serotypes. [17]
Phaffia rhodozyma
Johnson has also focused his research on Phaffia rhodozyma. Specifically,he initiated studies of astaxanthin formation in P. rhodozyma and identified optimal conditions for maximizing yeast and carotenoid production,contributing to advancements in astaxanthin production from P. rhodozyma. [18] He has also explored astaxanthin production in microorganisms and revealed the influence of environmental factors on carotenogenesis. [19] Additionally,he has optimized yeast cell preparation for enhanced astaxanthin production and deposition in salmonid diets, [20] [21]
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